JPH0339918A - Zoom lens for variable magnification copying machine - 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] [Industrial Application Field] The present invention relates to a zoom lens for a variable magnification copying machine, and more specifically, the present invention relates to a zoom lens for a variable magnification copying machine, and more specifically, the conjugate length (object-image distance) from the object plane to the imaging plane.
The present invention relates to a zoom lens suitable for changing the magnification while keeping the zoom constant.

[Conventional technology]

With the advent of copying machines, especially electrophotographic copying machines that use paper, it has become possible to carry out extremely efficient office processing. However, in recent years, as the needs for copying machines have diversified, the ability to obtain hard copies with the above-mentioned dimensional ratios changed, i.e., variable magnification to obtain enlarged copies and reduced copies. There is now a strong demand for this function to be provided.

In this case, there are various methods for the variable magnification function, and one example is one in which the variable magnification is performed using an equi-borrowed lens.

Specific methods for this example include changing the conjugate length from a fixed focal length lens to the object plane and the conjugate length from the lens to the imaging plane, that is, the object-to-image distance; Sometimes a converter lens is inserted into the optical path of a fixed focal length lens.

When changing the magnification by changing the conjugate length of the former, it is necessary to move a folding mirror, etc. to change the conjugate length, and the conjugate length is the minimum when the magnification is 1x, and the conjugate length is the minimum at 1x magnification. The further away from the lens, the longer it becomes, so if the variable magnification ranges over a wide range, for example from about 05x to about 2.0x, the amount of movement of the folding mirror etc. will become very large and the entire optical system will become larger. In addition to this drawback, there are also problems in that the number of component parts increases and a large number of particularly high-precision members are required.

In addition, when changing the magnification by inserting the latter converter lens, it goes without saying that only one magnification ratio can be changed with t converter lenses, and the frequently used magnification/reduction ratio 1, for example, 85 The enlargement/reduction size is specified because the magnification is changed in stages by preparing multiple converter lenses for enlarging the image to A4 size, reducing A3 size to A4 size, etc. In some cases, for example, although they can satisfy the requirements of copy size standardization and storage, they cannot completely meet the needs of users.In addition, these converter lenses are composed of at least two lenses. , is high in cost, and moreover, these must be prepared for a plurality of variable power stages, and the switching mechanism for these becomes complicated, resulting in an overall increase in cost.

For this reason, zoom lenses have been developed that change the magnification while keeping the conjugate length from the object plane to the image plane constant. As an example of such a zoom lens, Japanese Patent Laid-Open No. 61-
There is one described in the 151604% publication.

That is, in this optical system, the same lens groups as "concave lens, convex lens, concave lens" are arranged symmetrically on the object plane side and the image plane side with the aperture as the center, and the It is configured by arranging a sixth lens, and includes two fixed lens groups consisting of the first lens and the sixth lens, a first movable lens group consisting of the second lens and the third lens, and a fourth lens. It is composed of a total of four lens groups including a second movable lens group consisting of a fifth lens.

When the magnification is the same, the first to sixth lenses are positioned symmetrically on the object plane side and the image plane side, respectively, with the aperture as the center, and when the magnification is changed, the first and second movable lens groups are positioned symmetrically. Enlargement/reduction is performed by moving the aperture by an equal amount with the aperture as the center.

[Problem to be solved by the invention]

However, the variable power optical system described in JP-A No. 61-151604 has a dark FNα of about 11, and furthermore, the variable power system is variable by moving the movable group symmetrically around the diaphragm. Magnification range is 0.647 to 1.41
It had the disadvantage of being relatively narrow at four times the size.

Furthermore, when the magnification is close to 1.4 magnification, the amount of movement of each lens group is small, and as the magnification moves away from 1.0 magnification (enlargement side or reduction side), the amount of movement increases.
The amount of movement increases rapidly from around 14x (0.707x when reduced), so the movement of each group is moved symmetrically around the aperture, resulting in a change of about 0.5x to 2x. In order to achieve this high magnification, the distance between each group must be large, which means that the overall length of the lens becomes extremely long, and various imaging performances deteriorate significantly when changing magnification, especially at magnifications far from 100% magnification. There was a problem.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to increase the conjugate length from the object plane to the image plane by about 0.5 times while keeping it constant. It is an object of the present invention to provide a zoom lens for a variable magnification copying machine, which can obtain a wide range of magnification from 2.0 times to more than 2.0 times with a small number of lenses, and which does not increase in size or cause deterioration in image quality. .

[Means to solve the problem]

In order to achieve the above object, the invention of claim 1 includes, in order from the object plane toward the image plane, a first lens made of a concave lens with a concave surface facing the object side, a second lens made of a convex lens, and a second lens made of a convex lens. The third lens consists of a meniscus concave lens with a concave surface facing the side.
a lens, an aperture, a fourth lens that is the same lens as the third lens and has a concave surface facing the image plane side, a fifth lens that is the same lens as the second lens, and a fifth lens that is the same as the first lens. A zoom lens for a variable magnification copying machine with a configuration of 6 elements in 6 groups and a 6th lens with a concave surface facing the image plane side, when the object plane is imaged at the same magnification on the image plane. The first to sixth lenses are arranged symmetrically about the diaphragm, and when the object plane is magnified and imaged on the image plane, at least the first lens and the sixth lens are arranged as a fixed group. By moving at least the second lens and the fifth lens of the second to fifth lenses and the diaphragm asymmetrically and moving the entire lens system in the optical axis direction, the conjugate from the object plane to the image plane is obtained. The lens is characterized in that it is configured to enable continuous magnification while keeping the length constant regardless of whether the magnification is the same or variable.

In addition, in order to achieve the above-mentioned object, the invention of claim 2 provides the above-mentioned structure with the focal length of the first lens set to fl, the focal length of the third lens set to f3, and the entire lens system at the same magnification. When fO is the composite focal length of This feature is characterized in that it has a configuration in which it is added.

In addition, in order to achieve the above-mentioned object, the invention of claim 3 includes a first lens which is a concave lens having a concave surface facing the object side in order from the object plane to the image plane.

a second lens made of a convex lens, a third lens made of a concave lens with a concave surface facing the object side, an aperture, a fourth lens made of the same lens as the third lens and having a concave surface facing the image plane side; a fifth lens made of the same lens as the second lens;
A zoom lens for a variable magnification copying machine with a configuration of 6 elements in 6 groups, which includes a 6th lens that is the same as the first lens and has a concave surface facing the image plane side, and has an object plane of equal magnification. When forming an image on the image plane, the first to sixth lenses are arranged symmetrically about the aperture, and when the object plane is magnified and formed on the image plane, the first lens and the sixth lens are arranged symmetrically with respect to the aperture. The third lens, the fourth lens, and the sixth lens are set as a fixed group, and the second lens and the fifth lens are moved asymmetrically, and the entire lens system is moved in the optical axis direction. The lens is characterized in that it is configured to enable continuous magnification while keeping the conjugate length up to the plane constant regardless of whether it is the same magnification or variable magnification.

In addition, in the invention of claim 4, in order to achieve the above object, the focal length of the first lens is set to fL.
When the focal length of the second lens is f2 and the composite focal length of the entire lens system at equal magnification is fO, then 0.4< l fl/fo I <0.7 and 0.3 It is characterized by satisfying the following condition: <f2/f0|<0.4.5.

[For production]

In the zoom lens for a variable magnification copying machine according to claims 1 and 2 of the present invention, when the lens composed of 6 elements in 6 groups forms an image on the image plane at the same magnification, it is symmetrical about the aperture. the focal length fl (or f6) of the first (or sixth) lens and the focal length f3 (or f4) of the third (or fourth) lens with respect to the combined focal length fO of the entire lens system.
), 0.4<l ffl/f0|<0.650.7<I
On the other hand, when changing the magnification, at least the first lens and the sixth lens are fixed, and at least the second lens and the fifth lens are moved asymmetrically, so that the object is Continuous magnification is performed over a range of about 0.5 to 2 times while keeping the conjugate length from the surface to the image plane the same as when the magnification is the same.

By suppressing the upper limit of lfl/fo+ to 0.65, the amount of movement of the movable lens during zooming is avoided from increasing, and the entire lens system is made more compact. By suppressing the value to 0.4, large aberrations that tend to occur in the first lens and the sixth lens are prevented from occurring.

Furthermore, the upper and lower limits of lf3/fo+ are set to 1.4.
and 0.7 to prevent the Petzval sum from becoming too large or too small, suppressing the occurrence of astigmatism and field curvature as much as possible,
Prevents MTF deterioration.

In addition, in the zoom lens for a variable magnification copying machine according to claims 3 and 4 of the present invention, when the lens composed of 6 elements in 6 groups is focused on the image plane at the same magnification, the aperture is centered. The focal length of the first (or sixth) lens is fl (or f6) with respect to the combined focal length fO of the entire lens system.
) and the focal length f2 (or f5) of the second (or fifth) lens are as follows: 0.4<|fl/f0|<0.7 0.3<f2/f0|<0.45 On the other hand, when changing the magnification, the first. Third. 4th. By keeping the 6th lens fixed and moving the 2nd and 5th lenses asymmetrically, the conjugate length from the object plane to the image plane is kept the same as when it is 1x, and the magnification is about 0.5x to 2x. Continuous scaling is done over the range.

Then, by suppressing the upper limit of lfl/fo+ to 0.7,
This avoids increasing the amount of movement of the movable lens during zooming and makes the entire lens system more compact.
The lower limit of lfl/fol is suppressed to 0.4 to prevent large aberrations that tend to occur in the first and sixth lenses.

Furthermore, the upper and lower limits of f 2/f O are set to 0.3
and 0.45 to prevent the Petzval sum from becoming too large or small, suppressing the occurrence of astigmatism and field curvature as much as possible, and preventing deterioration of the MTF.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a zoom lens for a variable magnification copying machine according to claims 1 and 2 of the present invention will be described in detail with reference to the accompanying drawings.

First, the first embodiment of the present invention is shown in FIGS. 1 and 2 (A) to (
C), Figure 3 (A1) to (A3), Figure 3 (B1) to (
B3), Figures 3 (C1) to (C3) and Figure 4 (A)
-(C) and FIGS. 5(A)-(C).

FIG. 1 is a lens configuration diagram showing the basic configuration of a zoom lens. The object side, for example, the surface of a document in an electrophotographic copying machine, and the image side, for example, the exposed surface of an image carrier such as a photoreceptor drum. A zoom lens is inserted between the two. In this zoom lens, the first
The third to third lenses L1 to L3, the diaphragm, and the fourth to sixth lenses L4 to L6 are arranged. That is, the first lens L
1 is a biconcave lens or a meniscus concave lens (negative meniscus lens) formed by a concave surface of surface 1 and a concave or convex surface of surface 2 located on the object side, and a second lens L2 is a convex surface of surface 3 and a convex surface of surface 4. A convex lens (biconvex lens) formed by
The third lens L3 is a meniscus concave lens formed by a concave surface 5 and a convex surface 6, with the concave surface facing the object side, and an aperture located at surface 7 on the image surface side of this third lens L3. a is placed. The image plane side of this diaphragm a is formed by a convex surface 8, which is the same as the surface 6, and a concave surface 9, which is the same as the surface 5. A fourth lens L4 is arranged, which is a meniscus concave lens with a convex surface facing the object side. On the image plane side of the fourth lens L4, a fifth lens L5 is disposed, which is a convex lens formed by a convex surface 10 that is the same as the surface 4 and a convex surface 11 that is the same as the surface 3. has been done. On the image plane side of this fifth lens L5, the surface 2
A sixth lens L6 is disposed, which is a biconcave lens or a meniscus concave lens with a concave surface facing the image plane, which is formed by a concave or convex surface of the surface 12 that is the same as the surface 1, and a concave surface of the surface 13 that is the same as the surface 1. ing.

Furthermore, the radii of curvature r 1 to r 13 of surfaces 1 to 13, which are the forming surfaces of these first to sixth lenses L1 to L6, are
and the axial distance dl=cl12 between surfaces 1 to 13.

refractive index N1 to N6.

Atsube number v1~ v6 is The settings are as shown in Table 1 below.

Here, the first to sixth lenses L 1 to L as described above are shown in Table 1.
6 lenses, when the focal length of the first lens L1 is fl, the focal length of the third lens L3 is f3, and the combined focal length of the entire lens system at equal magnification is fO, then 0.4<fl/fo< 0.65, and satisfies the following conditions: 0.7<f3/f0|<1.4. That is, fl, f3
．． The respective values of fO are f 1 =-45, 3 f3 = -113, 9 fo = 100.0, so the value of lfl/fo+ is 0.45 and l
The value of f3/fo+ is 1.14.

Note that the first lens Ll, the sixth lens L6J, the third lens L3, and the fourth lens L4J are completely the same lenses (however, their orientations are opposite), so the focal length of the sixth lens L6 is f6. , even when the focal length of the fourth lens L4 is f4, it naturally satisfies the conditions of 0.4<f6/f0|<0.65 and 0.7<f4/f0|<1.4. The result is as follows.

fl/fol=　f6/fo+, and f3/fO=lf4/f0+.

Now, the above-mentioned 0.4<l f 1/f O+ <0.
65 or 0.4< I f 6/f O+ <0.6
The condition 5 determines the power of the first lens LL and the sixth lens L6, and the value of fl/fol=l f6/fo+ is the upper limit of 0.
If it exceeds 65, the amount of movement of the movable lens during zooming becomes large, making it impossible to make the entire lens system compact.

Furthermore, if the value of l fl/fOl=l f6/fOl falls below the lower limit of 0.4, very large aberrations will occur in the fixed lens group, that is, the first lens L1 and the sixth lens L6. In order to correct aberrations, the first lens L1
Therefore, the number of elements constituting the sixth lens L6 itself must be increased, leading to an increase in cost and making it impossible to make the entire lens system compact.

On the other hand, the aforementioned 0.7<I f 3/f O+ <1.
4 or 0.7<l f4/f0 +<1.4 is the condition that determines the power arrangement of the master lens formed by the third lens L3 and the fourth lens L4, and f3/fOl
=l When the value of f4/fO+ exceeds the upper limit of 0.7, the Petzval sum increases, the image plane shifts in the negative direction, and astigmatism (aberration) increases.

On the other hand, if the value of l f3/fOl=l f4/fO+ falls below the lower limit of 0.7, the Petzval sum becomes smaller, the image plane shifts in the positive direction, and the curvature of field increases.

Furthermore, if the value of l f3/fOl=l f4/fO+ exceeds the upper limit or falls below the lower limit, the balance between on-axis and off-axis will be lost, causing deterioration of MTF.

The on-axis spacing d2°d4. in FIG. 1 and Table 1 above. d
6. d7. d9. dll takes different values when the magnification is constant and when changing the magnification, in other words, the second to fifth lenses L2 to L5
moves as shown in Table 2.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Table 1, has a lens configuration diagram shown in Figure 2 ( A)
The lens configuration diagram at the same magnification (m=1.0) is shown in the second figure.
FIG. 2(B) shows the lens configuration at the time of reduction (m=0.5). FIG. 2(C) shows the lens configuration.

In this case, the first lens L1 and the sixth lens L6 are fixed lens groups as described above, and if we focus on the amount by which the second lens L2, which is located on the image plane side of the first lens L1, moves, the axial distance Focusing on d2, it changes from the time of enlargement (m = 2.0), to the time of original size (m = 1.0), and then to the time of reduction (m = 0.5).
), it changes from 1.443 to 0.233 to 1.007.

On the other hand, if we focus on the amount by which the fifth lens L5, which is located on the object plane side of the sixth lens L6, which is a fixed lens group, moves, that is, if we focus on the axial distance dll, we can see that when magnifying (m=2
．． 0) to the same size (m=1.0) to the reduced size (
m=0.5) from 1.007 to 0.2
It will change to 1.443 after passing through 33.

As is clear from comparing the two, at the same magnification (m=1
．． 0) The second lens L2 on the enlargement side and reduction side
, the fifth lens L5 move in opposite directions, and the amount of movement is the same.

On the other hand, the relationship between the movements of the third lens L3 and the fourth lens L4 (
The same thing can be said about the relationship between the on-axis distance d4 and the on-axis distance d9, and the relationship between the on-axis distance d6 and the on-axis distance d7.
The same can be said about the relationship between

Therefore, when forming an image of the object plane on the image plane at the same magnification, the first to sixth lenses L1 to L6 are arranged symmetrically about the aperture a, and change the magnification of the object plane to form an image on the image plane. When forming an image, the first lens L1 and the sixth lens L6
is a fixed group, and the second to fifth lenses L2 to L5 are moved by amounts that are symmetrical to each other during enlargement and reduction.

Naturally, as the zoom lens moves, the entire lens system moves in the optical axis direction between the object plane and the image plane, thereby achieving conjugate movement from the object plane to the image plane. It is possible to continuously change the magnification while keeping the length constant regardless of whether the magnification is the same or when the magnification is changed. The d-line (587, '56n
m) ■, F-line (486, 13nm) ■, CB (6
Figure 3 shows the spherical aberration diagram of (56, 27 nm)
A1), (B1) and (C1) show the d-line ■, F-line ■, and C of the sagittal ray and meridional ray, respectively.
The aberration diagrams of astigmatism of line ■ are shown in Fig. 3 (A2), (B2) and (C2), and the aberration diagram of distortion aberration is shown in Fig. 3 (A3).
), (B3) and (C3), respectively.

Similarly, regarding comatic aberration, d-line, F-line ■, C
Figure 4 (A) shows the aberration diagram when each line ■ is magnified (m = 2.0), and Figure 4 (B) shows the aberration diagram when it is at the same magnification (m = engineering, 0). FIG. 4(C) shows the aberration diagrams for 34.0 when the object height Y is 34.0 when the object is magnified (m=2.0).
5, at the same size (m = 1.0) and when reduced (m = 0.5
), the characteristic of 69.0 and 0.9Y 0
．． The characteristics of 75Y0.5Y, 0.25Y and on-axis are shown below. Furthermore, when expanding as described above (m=2
．． 0) At the same magnification (m=1-.0) and when reduced (m=
0.5) , respectively, are shown in FIGS. 5(A), (B), and (C).

In addition, in the aberration diagrams shown in FIGS. 3 (A1), (B1), and (CI) above, SA represents spherical aberration, SC represents sine condition,
The spherical aberration is shown by a solid line, and the sine condition is shown by a broken line.

In the aberration diagrams shown in FIGS. 3(A2), (B2), and (C2), DS and DM represent astigmatism, and among these, the sagittal ray is shown by a solid line, and the meridional ray is shown by a broken line, respectively.

In the aberration diagrams shown in FIGS. 3 (A3), (B3), and (C3), DIST indicates distortion aberration.

As is clear from the aberration diagrams above, the on-axis and off-axis aberrations are very well balanced at each magnification, and looking at the coma aberration, even though the aperture efficiency is almost 100%, there is no flare. It can be seen that the component is very small and has been well corrected.

Also, as seen from the spatial frequency vs. MTF characteristic curve, M
The TF characteristic has very high contrast not only when the image is at the same magnification, but also when it is enlarged and reduced, which means that the image quality of the final hard copy that is obtained is significantly improved.

Next, FIGS. 6(A), (B), and (C) show the second embodiment of the present invention in each state during enlargement, same size, and reduction.
), Figure 7 (A1) to (A3), Figure 7 (B1) to (B
3) and Figures 3 (C1) to (C3), Figure 8 (A),
(B) and (C), Figure 9 (A), (B) and (C)
). In this embodiment, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 3 below.

Table 3 also shows the axial distance d2 between the first lens L1- to the sixth lens L6, each of which is set as shown in Table 3. d
4. d6. d7. d9. dll is changed according to each magnification as shown in Table 4 below.

The first part is set as shown in Tables 3 and 4.
The zoom lens formed by the sixth lenses L1 to L6, etc., is shown in the lens configuration diagram at the time of magnification (m=2.0).
The lens configuration diagram shown in Figure (A) at 1-magnification (m = 1.0) is shown in Figure 6 (B), and when reduced (m = 0.5).
A lens configuration diagram is shown in FIG. 6(C).

In this embodiment, similarly to the first embodiment described above, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is changed continuously. You can get a zoom lens.

In addition, in the same way as described above, the corresponding spherical aberrations are shown in the lens configuration diagrams at the time of enlargement, the same magnification, and the time of reduction in the second embodiment shown in FIGS. 6(A), (B), and (C), respectively. The aberration diagrams are shown in Figure 7 (Ai), (B1) and (C1), the aberration diagrams of astigmatism are shown in Figure 7 (A2), (B2) and (C2), and the aberration diagrams of distortion aberration are shown. Figure 7 (A3
), (B3) and (C3).

Similarly, regarding coma aberration, Figures 8 (A,) and (B)
) and (C), and similarly dimensional MTF curves are shown in FIGS. 9(A), (B), and (C).

Next, FIGS. 10 (A), (B) and (
C), Figure 11 (Al) to (A3), Figure 11 (B1)
- (B3) and Fig. 11 (C1) - (C3), 12th
Figures (A), (B') and (C), Figure 13 (A), (
This will be explained using B) and (C). In this embodiment, each part of the first or 1L sixth lenses L1 to L6 is configured as shown in Table 5 below.

Also, as shown in Table 5, the axial distance d2 between the first lens LL to the sixth lens L6 is set. d4
．． dB, d7. d9. dll is changed according to each magnification as shown in Table 6 below.

The first part is set as shown in Tables 5 and 6.
The zoom lens formed by the sixth lenses L, 1 to L6, etc., is shown in FIG. 10(A) in a lens configuration diagram when it is magnified (m=2.0), and when it is magnified (m=1.0). 0) is shown in Figure 10 CB), and when reduced (m=0.5
) is shown in FIG. 10(C).

In this embodiment, as in the above embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether it is the same magnification or variable magnification, and the magnification is changed continuously. You can get a zoom lens for aircraft.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to enlargement, same-magnification, and reduction shown in FIGS. Shown in Figure 11 (Al), (B1) and (C1),
The aberration diagrams of astigmatism are shown in Fig. 11 (A2), (B2) and (C2), and the aberration diagram of distortion aberration is shown in Fig. 1 (A3).
, (B3) and (C3).

Similarly, coma aberration is also shown in Figures I2 (A), (B) and (C) in correspondence with magnification, same magnification and reduction.
), and similarly diometric MTF curves are shown in FIGS. 13(A), (B), and (C), respectively.

Next, FIG. 14(A) shows the fourth embodiment of the present invention in each state when it is enlarged, when it is the same size, and when it is reduced.

(B) and (C), Figures 15 (A1) to (A3), Figures 15 (B1) to (B3), and Figures 15 (C1) to (
C3), Figure 16 (A), CB) and (C), Figure 17
This will be explained using figures (A), (B) and (C). In this embodiment, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 7 below.

Table 7 also shows the axial distance d2 between the first lens L1 to the sixth lens L6, each of which is set as shown in Table 7. d4
．． d6. d7. d9. dll is.

It can be varied as shown in Table 8 below.

The first part with each part set as shown in Tables 7 and 8.
The zoom lens formed by the first to sixth lenses L1 to L6, etc., is shown in the first lens configuration diagram at the time of magnification (m=2.0).
The lens configuration is shown in FIG. 4(A), and the lens configuration diagram at the same magnification (m=1.0) is shown in FIG. 14(B), and when reduced (m=0.
5) A lens configuration diagram is shown in FIG. 14(C).

In this embodiment, similarly to each of the above-mentioned embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is continuously changed. A lens is obtained.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to the magnification, 5 equal magnification, and reduction, shown in FIGS. Figure 15 (Al)+' (B1) and (C1) show the astigmatism, and Figure 15 (A2), (B2) and (C
2), and the aberration diagrams of distortion aberration are shown in Fig. 15 (A3), (
B3> and (C3).

Similarly, regarding coma aberration, Fig. 16 (A) CB)
17(A), (B) and (C) show geometrical MTF curves in the same manner.

Next, FIGS. 18 (A), (B) and (
C), Figure 19 (A1) - (A3) (Bl) - (B3)
and (C1) to (C3), FIG. 20 (A), (B) and (C), and FIG. 21 (A), (B) and (C).

In this embodiment, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 9 below.

Table 9 also shows the axial distance d2 between the first lens L1 to the sixth lens L6 whose respective parts are set as shown in Table 9. d4
．． d6. d7. d9. dll is changed as shown in Table 10 below.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Tables 9 and 10, has a lens configuration diagram when magnified (m = 2.0). 18th
Figure 18 (A) shows the lens configuration diagram at the same magnification (m = 1.0), and Figure 18 (B) shows the lens configuration diagram at the time of reduction (m = 0.5).
) is shown in FIG. 18(C).

In this embodiment, similarly to each of the above-mentioned embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is continuously changed. A lens is obtained.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to enlargement, same-magnification, and reduction shown in FIGS. Shown in Figure 19 (Al), (B1) and (C1),
Aberration diagrams of astigmatism are shown in Fig. 19 (A2), (B2) and (C2), and aberration diagrams of distortion aberration are shown in Fig. 19 (A3).
), (B3) and (C3).

Similarly, regarding coma aberration, see Figure 20 (A) and (B).
21 (A), (B) and (C), respectively.

Next, FIGS. 22A, 22B, and 22A show the sixth embodiment of the present invention in each state when it is enlarged to the same size and when it is reduced.
C), Figure 23 (A1) - (A3) (B1) - (B3)
and (C1) to (C3) will be explained using FIGS. 24 (A), (B) and (C) and FIG. 25 (A), (B) and (C).

In this embodiment, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 11 below.

Table 1: On-axis spacing d2 in Table 11 above. d4゜d9.
dll takes different values when the magnification is constant and when the magnification is varied. In other words, the second to fifth lenses L2 to L5 move as shown in Table I2.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Tables 11 and 12, has a lens configuration diagram when magnified (m = 2.0). Second
The lens configuration is shown in FIG. 2(A), and the lens configuration diagram at the same magnification (m=1.0) is shown in FIG. 22(B), and when reduced (m=0.
5) A lens configuration diagram is shown in FIG. 22(C).

In this embodiment, similarly to each of the above-mentioned embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is continuously changed. A lens is obtained.

In addition, in this sixth embodiment, the axial distance d6 between the surface 6 forming the third lens L3 and the aperture, and the axis between the aperture and the surface 8 forming the fourth lens L4 from the aperture. Upper interval d
7 is fixed at 0.341. Therefore,
Zoom movement is performed by moving only the second lens L2 and the fifth lens L5, and the first lens L1, third lens L3, fourth lens L4, and sixth lens L6 form a fixed lens group.

Furthermore, they are shown in FIGS. 22(A), (B), and (C), respectively. The 23rd aberration diagram of the spherical aberration corresponding to the lens configuration diagram at magnification, normal magnification, and reduction is shown in the same way as above.
Figures (A1), (B1) and (C1) show the aberration diagrams of astigmatism in Figure 23 (A2), (B2) and (C2).
The aberration diagrams of distortion aberration are shown in Fig. 23 (A3) and (B3).
) and (C3).

Similarly, regarding coma aberration, see Figure 24 (A) and (B).
25 (A), (B) and (C) show geometrical MTF curves in the same manner.

In the above first to sixth embodiments, the above-mentioned conditions, that is, 0.4<l f 1/f O+ <0.65 and 0.7<f3/f0|<1.4 are satisfied. Of course, it is like this,
These values are shown in Table 13 below.

As is clear from Table 13 above, it can be seen that the above conditions are satisfied in all the examples.

Next, embodiments of the zoom lens for a variable magnification copying machine according to the invention of claim 3 and the invention of claim 4 will be described in the seventh embodiment to the first embodiment.
This will be explained in detail as one example.

First, the seventh embodiment is shown in FIGS. 26 and 27 (A) to (C).
, Fig. 28 (A1) to (A3), Fig. 28 (Bl) to (
B3), Figure 28 (C1) to (C3), Figure 29 (A)
This will be explained using (C).

FIG. 26 is a lens configuration diagram showing the basic configuration of the zoom lens according to claims 3 and 4, in which the zoom lens is inserted between the object plane side and the image plane side as described above. In the zoom lens, the first to third lenses L1 to L3, the aperture a, and the fourth to sixth lenses L4 to L6 are arranged in order from the object plane toward the image plane. That is, the first lens L
1 is a biconcave lens formed by a concave surface L located on the object side and a concave surface 2, and the second lens L2 is a convex lens (biconvex lens) formed by a convex surface 3 and a convex surface 4. , the third lens L3 is a meniscus concave lens formed of a concave surface 5 and a convex surface 6, with the concave surface facing the object side, and an aperture a located on the surface 7 on the image plane side of the third lens L3. is located. On the image plane side of this diaphragm a, there is a meniscus concave lens with the convex surface facing the object side, which is formed by a convex surface 8 which is the same as the above surface 6 and a concave surface 9 which is the same as the above surface 5. A fourth lens L4 is arranged.

On the image plane side of the fourth lens L4, there is a fifth lens L5 which is a convex lens formed by a convex surface 10 which is the same as the surface 4 and a convex surface 11 which is the same as the surface 3. It is located. The image plane side of the fifth lens L5 is formed by a concave surface 12 which is the same as the surface 2, and a concave surface 13 which is the same as the surface 1. A sixth lens L6, which is a biconcave lens with a concave surface facing the image plane side, is arranged.

Furthermore, the radii of curvature r 1 to r 13 of surfaces 1 to 13, which are the forming surfaces of these first to sixth lenses L1 to L6, are
, the axial spacing d1 to d12 of surfaces 1 to 13, and the refractive index N1
~N6 and the Atsube numbers vl~v6 are set as shown in Table 14 below, and the zoom movement is controlled by the second lens L2.
and by moving only the fifth lens L5,
The first lens L1, the third lens L3, the fourth lens L4, and the sixth lens L6 form a fixed lens group.

Table 14 Here, the first to sixth lenses L1 to L6 as described above are
In the lens, when the focal length of the first lens LL is fl, the focal length of the second lens L2 is f2, and the composite focal length of the entire lens system at equal magnification is fO, then 0.4<fl/f0|< 0.7, and satisfies the following conditions: 0.3<f 2 /f 0 |<0.45. That is, fl, f2
．． The respective values of fO are fl=-97,26 f2=68.2 fo=190.02, so the value of lfl/fo+ is 0.51°2 and the value of f2/fO is 0.359. It is.

In addition, "the first lens L1, the sixth lens L6J, and the "second lens
Each of the lens L2 and the fifth lens L5J is the exact same lens (however, the directions are opposite), so the sixth lens
Naturally, when the focal length of the lens L6 is fif6 and the focal length of the fifth lens L5 is f5, it is 0.4. < I f6/ f Ol <0.7 and satisfies the conditions of 0.3 < f 5/f 0 | < 0.45, and as a result, f
1/fOl=l f6/fO+ and f2/fO=f5/fO.

Now, the above-mentioned 0.4<l f 1/f O+ <0.
7 or 0.4<l f 6/f O+ <0.7, the power of the fixed group added to the master lens,
That is, the first lens L1 as a fixed group added to the outside of the second lens L2 to fifth lens L5 as a master lens.
and determines the power of the sixth lens L6, and the value of fl/fol=lf6/fo+ is the upper limit of 0.7
If it exceeds , the amount of movement of the movable lens during zooming becomes large, making it impossible to make the entire lens system compact.

If the lfl/fol=If6/fo+(7) value falls below the lower limit of 0.4, very large aberrations will occur in the fixed lens group, that is, the first lens L1 and the sixth lens L6. In order to correct this, it is necessary to increase the number of lenses in the fixed lens group, ie, the first lens L and the sixth lens L6, which increases the cost and makes it difficult to make the entire lens system more compact. become unable.

On the other hand, the aforementioned 0.3<f2/f0|<0.45 or 0
．． The condition 3<f5/f0|<0.45 determines the power arrangement of the master lens formed by the second lens L2 to the fifth lens L5, and the value of f2/fO=f5/fO is the upper limit value. If it exceeds 0.45, the Petzval sum increases, the image plane shifts in the negative direction, and astigmatism (aberration) increases.

Also, f2/fo=f5/fcl) value is the lower limit of 0.3
If the value is less than , the Petzval sum becomes smaller, the image plane shifts in the positive direction, and the curvature of field becomes larger.

Furthermore, if the value of f2/fo=f5/fO exceeds the above-mentioned upper limit or falls below the lower limit, the balance between on-axis and off-axis will be lost, causing deterioration of MTF.

On-axis spacing d2, d4 in FIG. 26 and Table 14 above
．． d9. dll takes different values when magnifying 1 and when changing magnification,
In other words, the second lens L2 and the fifth lens L5 are the 15th lens L2 and the 5th lens L5.
They move as shown in the table.

1st to 6th sections with each part set as shown in Table 14
The zoom lens formed by lenses L1 to L6, etc. is shown in Figure 27 (A) when it is expanded (m = 2.0).
The lens configuration diagram at the same magnification (m=1.0) is shown in the second figure.
7(B), and a lens configuration diagram at the time of reduction (m=0.5) is shown in FIG. 27(C).

In this case, the first lens L1, the third lens L3, the fourth lens L4, and the sixth lens L6 are fixed lens groups as described above, and the second lens L is located on the image plane side of the first lens L1.
If we focus on the amount by which 2 moves, that is, on-axis spacing d2, we can see from the magnification (m=2.0) to the same magnification (m=1.0)
3.9 during the time of reduction (m=0.5)
It will change from 42 to 2.655 through 1.0 k8.

On the other hand, if we focus on the amount by which the fifth lens L5, which is located on the object plane side of the sixth lens L6, which is a fixed lens group, moves, that is, if we focus on the axial distance dll, we can see that when magnifying (m=2
．． 0) to the same size (m=1.0) to the reduced size (
m=0.5) from 2.655 to 1.0
After passing through 18, it changes to 3.942.

As is clear from comparing the two, at the same magnification (m=1
．． 0) The second lens L2 on the enlargement side and reduction side
, the fifth lens L5 move in opposite directions, and the amount of movement is the same.

Therefore, when forming an image of the object plane on the image plane at the same magnification, the first to sixth lenses L1 to L6 are arranged symmetrically about the aperture a, and change the magnification of the object plane to form an image on the image plane. When forming an image, the above-mentioned 1. 3rd, 4th. 6th lens Ll,
L3. L4. L6 is a fixed group, and the second lens L2 and the fifth lens L5 are moved by amounts that are symmetrical to each other during enlargement and reduction. .

Naturally, as the zoom lens moves, the entire lens system moves in the optical axis direction between the object plane and the image plane, thereby achieving conjugate movement from the object plane to the image plane. It is possible to continuously change the magnification while keeping the length constant regardless of whether it is the same magnification or variable magnification.

In addition, the d-line (587, 56n
m) ■, C line (656, 27 nm) ■, F line (486,
Figure 28 (Al) shows the aberration diagram of spherical aberration of 13 nm) ■.
(B1) and (C1), and the aberration diagrams of astigmatism of the d-line ■, C-line ■, and F-line ■ of the sagittal ray and meridional ray, respectively, are shown in Fig. 28 (A2), (B2) and (
C2), and the aberration diagram of distortion aberration is shown in FIG. 28 (A3).

(B3) and (C3) respectively.

Similarly, regarding comatic aberration, di■, C-line■, F
Figure 29 (A) shows the aberration diagram when IIA■ is magnified (m = 2.0), and Figure 29 (B) shows the aberration diagram when it is at the same magnification (m = 1.0). When reduced (m=0.5
) are shown in Fig. 29 (C), and each time the object height Y is 74.25 when magnified (m = 2.0) and 74.25 when the object is magnified (m = 1.0). and when reduced (
When m=0.5), the characteristic of 148.5 and 0.9
The characteristics of Y, 0.75YO, 5Y, 0.25Y and each on the axis are shown.

In addition, the above FIG. 28 (A1), (B1) and (C1)
In the aberration diagrams shown in , SA represents spherical aberration, SC represents sine condition, and the spherical aberration is shown by a solid line, and the sine condition is shown by a broken line.

In the aberration diagrams shown in FIGS. 28 (A2), (B2) and (C2), DS and DM represent astigmatism, of which sagittal rays are shown by solid lines and meridional rays are shown by broken lines, respectively.

In the aberration diagrams shown in FIGS. 28 (A3), (B3), and (C3), DIST indicates distortion aberration.

As is clear from the aberration diagrams above, the on-axis and off-axis aberrations are very well balanced at each magnification, and looking at the coma aberration, even though the aperture efficiency is almost 100%, there is no flare. It can be seen that the component is very small and has been well corrected.

Next, FIGS. 30 (A), (B) and (
C), Figure 31 (A1) to (A3), Figure 31 (B1)
- (B3) and Fig. 31 (C1) - (C3), Fig. 32
This will be explained using figures (A), (B) and (C). This example is.

Each part of the first to sixth lenses L1 to L6 is the 36th lens below.
It is configured as shown in the table.

Table 6 Also, as shown in Table 16, the axial distance d2 between the first lens L1 to the sixth lens L6 is set as shown in Table 16. d
4. d9. dll is changed according to each magnification as shown in Table 17 below.

The zoom lens formed by the first to sixth lenses I, 1 to L6, etc. whose respective parts are set as shown in Tables 16 and 17 has a lens configuration at the time of magnification (m=2.0). The figure is shown in Figure 30 (A) at 1-1 magnification (rr+=1.0)
The lens configuration diagram is shown in FIG. 30 (B), and when reduced (m
-0,5) is shown in FIG. 30(C).

In this embodiment, similarly to the seventh embodiment, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is changed continuously. You can get a zoom lens.

In addition, in the same manner as described above, the corresponding spherical aberrations are shown in the lens configuration diagrams at the time of enlargement, same magnification, and reduction in the eighth embodiment shown in FIGS. 30(A), (B), and (C), respectively. The aberration diagrams are shown in Figure 31 (A1), (B1) and (C1).
), and the aberration diagrams of astigmatism are shown in Figure 31 (A2) and (B
2) and (C2), and the aberration diagram of distortion aberration is shown in the 31st
Shown in Figures (A3), (B3) and (C3).

Similarly, regarding coma aberration, see Fig. 32 (A) and (B).
and (C).

Next, Figures 33 (A), (B) and (C) and Figures 34 (A1) to (A3)' show the ninth embodiment in each state when it is enlarged, at the same size, and when it is reduced. , Fig. 34 (B1) to (B
3) and Figures 34 (C1) to (C3), Figure 35 (A
), (B) and (C). In this embodiment, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 18 below.

Table 8 Also, the axial distance d2 between the first lens L1 to the sixth lens L6 whose respective parts are set as shown in Table 18. d
4. d9. dll is changed according to each magnification as shown in Table 19 below.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Tables 18 and 19, has a lens configuration diagram at the time of magnification (m = 2.0). Third
The lens configuration is shown in Fig. 3(A), and the lens configuration diagram at the same magnification (m = 1.0) is shown in Fig. 33(B), and when reduced (m = 0).
, 5) is shown in FIG. 33(C).

In this embodiment, as in the above embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether it is the same magnification or variable magnification, and the magnification is changed continuously. You can get a zoom lens for aircraft.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to enlargement, same-magnification, and reduction shown in FIGS. 34 shown in Figures (Al), (Bl) and (C1),
The aberration diagrams of astigmatism are shown in Fig. 34 (A2), (B2) and (C2), and the aberration diagram of distortion aberration is shown in Fig. 34 (A3).
, (B3) and (C3).

Similarly, regarding comatic aberration, Fig. 35 (A), (B), and (C
) are shown respectively.

Next, FIGS. 36(A), (B), and (C) show the tenth embodiment in each state when it is enlarged, when it is the same size, and when it is reduced.
Figure 37 (A1) to (A3), Figure 37 (B1) to (B
3) and Figures 37 (C1) to (C3), Figure 38 (A
), (B) and (C). In this embodiment, each part of the first to sixth lenses LIL-L6 is
It is configured as shown in Table 0.

Table 0 Also, the on-axis distance d2. d
4. ．． d9. dll is changed as shown in Table 21 below.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Table 20 and the second upper table, is a lens configuration diagram at the time of magnification (m = 2.0). is the 36th
The lens configuration diagram shown in Figure 36 (A) is shown at the same magnification (m = 1.0) and is shown in Figure 36 (B) when it is reduced (m = 0.5).
A lens configuration diagram is shown in FIG. 36(C).

In this embodiment, similarly to each of the above-mentioned embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is continuously changed. A lens is obtained.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to enlargement, same-magnification, and reduction shown in FIGS. 37 shown in Figures (A1), (B1) and (C1),
Astigmatism is shown in Figure 37 (A2), (B2) and (C2).
The aberration diagrams of distortion aberration are shown in Fig. 37 (A3) and (B3
) and (C3).

Similarly, regarding coma aberration, Fig. 38(,A)(
Shown in B) and (C).

Next, Figures 39 (A), (B) and (C), and Figures 40 (A1) to (A1) showing the eleventh embodiment of the present invention in each state during enlargement, same size and reduction. A3) (B1) ~ (B3
) and (C1) to (C3).

This will be explained using FIGS. 41(A), (B) and (C). In this example, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 22 below.

Table 22 Also, the axial distance d2 between the first lens L1 to the sixth lens L6, each of which is set as shown in Table 22. d
4. d9. dll is changed as shown in Table 23 below.

The zoom lens formed by the first to sixth lenses L1 to L6, etc. whose parts are set as shown in Tables 22 and 23, has a lens configuration diagram at the time of magnification (m = 2.0). Third
The lens configuration diagram shown in FIG. 9(A) when the magnification is 1 (m=1.0) is shown in FIG. 39(B), and when it is reduced (m=0.
5) A lens configuration diagram is shown in FIG. 39(C).

In this embodiment, similarly to each of the above-mentioned embodiments, the conjugate length from the object plane to the image plane is kept constant regardless of whether the magnification is the same or when the magnification is changed, and the magnification is continuously changed. A lens is obtained.

In addition, the aberration diagrams of spherical aberration corresponding to the lens configuration diagrams corresponding to magnification, same-magnification, and reduction shown in FIGS. 39(A), (B), and (C) in the same manner as described above are Shown in Figure 40 (Al), (Bl) and (C1),
Aberration diagrams of astigmatism are shown in Fig. 40 (A2), (B2) and (C2), and aberration diagrams of distortion aberration are shown in Fig. 40 (A3).
), (B3) and (C3).

Similarly, regarding coma aberration, see Fig. 41 (A) and (B).
and (C).

Next, FIG. 42 (A) shows the I2th embodiment in each state at 268x and 2.0x enlargement, 11x magnification, and 0.5x and 0.36x reduction; CB), (C) and C
D), (E), Figure 43 (Al-A3), (Bl~B3
), (C1-C3) and (DI-D3), (El-E
3) and Figure 44 (A), (B), (C) and (D), (
This will be explained using E). In this example, each part of the first to sixth lenses L1 to L6 is configured as shown in Table 24 below.

Table 24 On-axis spacing d2 in Table 24 above. d4゜d9. d
ll takes a different value when the magnification is constant and when changing the magnification. In other words, the second lens L2 and the fifth lens L5 move as shown in Table 25.

The zoom lens formed by the first to sixth lenses L, 1 to L6, etc. whose parts are set as shown in Tables 24 and 25 has a lens configuration diagram with a variable magnification of 2.8x. A lens configuration diagram shown in FIG. 42(A) and with a magnification of 2°0x is shown in FIG. 42(B), and similarly, the magnification is 1°0x, 0.5x, etc.
Figure 42 (C
), (D), and (E). In this embodiment as well, in the same manner as in each of the above-mentioned embodiments, a zoom lens for a variable magnification copying machine that continuously changes magnification while keeping the conjugate length from the object plane to the image plane constant regardless of the magnification ratio can be obtained. .

Also, FIGS. 42 (A), (B), (C) and (D),
When magnified (2°8x, 2.0
magnification), normal magnification and reduced magnification (0.5 magnification).

43 (A1), (B1), (
C1), (Dl), and (El), and the aberration diagrams of astigmatism are shown in Fig. 43 (A2), (B2), (C2), and (
B2), (B2) and the aberration diagrams of distortion aberration are shown in Fig. 43 (A3), (B3), (C3) and (B3), (B3).
).

Similarly, regarding coma aberration, when magnified by 2.8 times (
Object height Y = 53.04), when magnified 2.0 times (Y = 74
．． 25), at the same magnification (Y = 148.5), at 0.5x reduction (Y = 148.5), and at 0°36x reduction (Y
=148.5) are shown in Figure 44 (A) and
Shown in (B), (C), (D), and (E).

In the above seventh to twelfth embodiments, the above-mentioned claims (
The conditions corresponding to 4), that is, 0.4<l f 1/f Ol <O07 and 0.3<f 2/f 0|<0.45 are satisfied. Of course,
These values are shown in Table 26 below.

As is clear from Table 26 above, the seventh embodiment to the first embodiment
It can be seen that the above conditions are satisfied in all of the two examples.

It should be noted that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

For example, in the above description, an example was shown in which the present invention is applied to a variable-magnification copying machine, but it can naturally be applied to a plate-making machine that has the same functional parts as a copying machine, and in this sense, a plate-making machine is also a copying machine. It belongs to the simplification of .

Moreover, especially in the 10th to 12th embodiments, f↓/f
The lower limit values of o+ and f2/fO are as follows.

Even if they are 0.35 and 0.25, respectively, the above-mentioned effects can be achieved.

〔Effect of the invention〕

As is clear from the above explanation, according to the zoom lens for a variable magnification copying machine according to the present invention, the conjugate length from the object plane to the image plane is kept constant, and the zoom lens can be adjusted from 0.36 times to 2.8 times. Since a variable magnification ratio can be obtained over a wide range of , there is no need for a conventional mechanism for driving a folding mirror or the like in conjunction with zoom movement, and the configuration of the variable magnification copying machine can be simplified.

In addition, the zoom lens itself does not become larger or the image quality deteriorates, and the lens structure can be made compact with 6 elements in 6 groups, allowing high image quality to be maintained not only at 1-magnification but also at enlargement and reduction.

In other words, as is clear from the aberration diagrams showing the aberrations of each example, the balance between on-axis and off-axis characteristics is very good in all examples, not only when magnified but also when enlarged and reduced. Looking at the coma aberration, it can be seen that although the aperture efficiency is approximately 100%, the flare component is very small and is well corrected. Furthermore, the MTF has extremely high contrast not only when magnified but also when enlarged and reduced, which significantly improves the image quality of the final hard copy.

Moreover, since the zoom lens is constructed using three pairs of identical lenses, it is advantageous in terms of manufacturing and manufacturing control.
In particular, it greatly contributes to cost reduction.

[Brief explanation of drawings]

FIG. 1 is a lens configuration diagram showing the basic configuration of a zoom lens for a variable magnification copying machine according to the invention of claims 1 and 2, and FIG.
) to (C) to Fig. 5 (A) to (C), respectively,
This is a diagram for explaining the first embodiment of the present invention, among which:
Fig. 2 (A) is a lens configuration diagram showing the optical path when magnifying, Fig. 2 (B) is a lens configuration diagram showing the optical path when magnifying the same, and Fig. 2 (C) shows the optical path when reducing the magnification. The lens configuration diagrams shown in FIG. 3 (A1), (A2), and (A3) are as follows:
FIG. 3 (Bl) is an aberration diagram showing spherical aberration, astigmatism, and distortion at the time of magnification. (B2) and (B3) are spherical aberrations at 5 equal magnification,
Aberration diagrams showing astigmatism and distortion, respectively. Figures 3 (C1), (C2), and (C3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, during reduction, and Figure 4 (A) is an aberration diagram showing comatic aberration during enlargement. Figure 4(B) is an aberration diagram showing comatic aberration when magnified, Figure 4(C) is an aberration diagram showing comatic aberration when zoomed out, and Figure 5(A) is an aberration diagram showing comatic aberration when magnified. A characteristic diagram showing the MTF curve. Figure 5 (B) is a characteristic diagram showing the MTF curve at 1 times magnification. Figure 5 (C) is a characteristic diagram showing the MTF curve at the time of reduction.
Characteristic diagrams showing the F curve, Figures 6 (A) to (C) to 9
Each of Figures (A) to (C) is a diagram for explaining the second embodiment of the present invention, and among these, Figure 6 (A) is a lens configuration diagram showing the optical path during expansion; Figure (B) is
Lens configuration diagram showing the optical path at the same magnification, Figure 6 (C)
is a lens configuration diagram showing the optical path during reduction, Fig. 7 (
A1), (A2), and (A3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, when magnified. Figure 7 (B1), (B2), and (B3) are aberration diagrams when magnified. Aberration diagram showing spherical aberration, astigmatism, and distortion, 7th
Figures (C1), (C2), and (C3) are aberration diagrams showing spherical aberration, astigmatism, and distortion at the time of reduction, respectively, and Figure 8 (A) is an aberration diagram showing coma aberration at the time of expansion,
Figure 8 (B) is an aberration diagram showing coma aberration when the magnification is the same, Figure 8 (C) is an aberration diagram showing coma aberration when being reduced, and Figure 9 (A) is an aberration diagram showing the coma aberration when being magnified. FIG. 9(B) is a characteristic diagram showing the MTF curve at the same magnification, FIG. 9(C) is a characteristic diagram showing the MTF curve at the time of reduction, and FIGS. 10(A) to (C ) to FIGS. 13(A) to (C) are diagrams for explaining the third embodiment of the present invention, among which FIG. 10(A) shows the lens configuration showing the optical path during magnification. Figure 10 (B) is a lens configuration diagram showing the optical path at the same magnification, Figure 10 (
C) is a lens configuration diagram showing the optical path during reduction, the first
1. Figures (Al), (A2), and (A3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, during magnification. Figures 11 (B1), (B2), and (B3) are Aberration diagrams (C1), (C2), and (C3) showing spherical aberration, astigmatism, and distortion at magnification, respectively, show spherical aberration, astigmatism, and distortion at magnification. 12(A) is an aberration diagram showing comatic aberration when magnified, FIG. 12(B) is an aberration diagram showing comatic aberration when magnified, and FIG. 12(C) is an aberration diagram showing comatic aberration when magnified. 13(A) is a characteristic diagram showing the MTF curve when magnified. FIG. 13(B) is a characteristic diagram showing the MTF curve when magnified. C) is a characteristic diagram showing the MTF curve during reduction, and Fig. 14 (
Each of A) to (C) to FIG. 17 (A) to (C) is a diagram for explaining the fourth embodiment of the present invention, and among these, FIG. FIG. 14 (B) is a lens configuration diagram showing the optical path at the same magnification, FIG. 14 (C) is a lens configuration diagram showing the optical path at the time of reduction, and FIG. 15 (A1) , (A2),
(A3) is an aberration diagram showing spherical aberration, astigmatism, and distortion at the time of magnification, and Fig. 15 (Bl) and (B2
) (B3) is an aberration diagram showing spherical aberration, astigmatism, and distortion at 1 magnification, respectively, and Fig. 15 (C1), (C
2) and (C3) are aberration diagrams showing respectively spherical aberration, astigmatism, and distortion at the time of reduction, and FIG. 16(A) is
Aberration diagram showing coma aberration during magnification, Figure 1.6 (B
) is an aberration diagram showing coma aberration at the same magnification, FIG. 16(C) is an aberration diagram showing coma aberration at reduction, and FIG.
Figure 7 (A) is a characteristic diagram showing the MTF curve when enlarged, Figure 17 (B) is a characteristic diagram showing the MTF curve when magnified, and Figure 17 (C) is a characteristic diagram showing the MTF curve when reduced. The characteristic diagrams shown in FIGS. 18(A) to 21(C) to 21(A) to (C) are diagrams for explaining the fifth embodiment of the present invention. (A) is a lens configuration diagram showing the optical path when magnifying, FIG. 18(B) is a lens configuration diagram showing the optical path when magnifying the same size, and FIG. 1-8(C) shows the optical path when reducing the magnification. Lens configuration diagrams, Figures 19 (A1), (A2), and (A3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, during magnification, Figures 19 (B1), (B2), and (B3). ) are aberration diagrams showing the spherical aberration, astigmatism, and distortion at the same magnification, and Figure 19 (C1), (C2), and (C3) show the spherical aberration, astigmatism, and distortion at the time of reduction. 20(A) is an aberration diagram showing comatic aberration at magnification, FIG. 20(B) is an aberration diagram showing comatic aberration at same magnification, and FIG. 20(C) is an aberration diagram showing comatic aberration at equal magnification. . Aberration diagram showing coma aberration during reduction, Fig. 21 (A)
is a characteristic diagram showing the MTF curve during expansion, No. 21-
Figure (B) is a characteristic diagram showing the MTF curve at 1 magnification,
FIG. 21(C) is a characteristic diagram showing the MTF curve during reduction, FIG. 22(A) to (C) to FIG. 25(A) to
Each of (C) is a diagram for explaining the sixth embodiment of the present invention, among which, FIG. 22(A) is a lens configuration diagram showing the optical path during expansion, and FIG. 22(B) is a diagram showing the lens configuration. , a lens configuration diagram showing the optical path at the same magnification, FIG. 22(C) is,
FIG. 23 (A1), (A2), and (A3) are lens diagrams showing the optical path during reduction. Aberration diagrams showing spherical aberration, astigmatism, and distortion at magnification, and Figures 23 (B1), (B2), and (B3) show aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, at equal magnification. Figure 23 (C1), (C2), (C3
) is an aberration diagram showing spherical aberration, astigmatism, and distortion at the time of reduction, FIG. 24(A) is an aberration diagram showing coma aberration at time of enlargement, and FIG. 24(B) is an aberration diagram showing the coma aberration at the time of magnification. FIG. 24(C) is an aberration diagram showing comatic aberration at the time of reduction. FIG. 25(A) is an aberration diagram showing comatic aberration at the time of reduction.
Characteristic diagram showing the MTF curve during expansion, Fig. 25 (B
) is a characteristic diagram showing the MTF curve at the same magnification, No. 25
Figure (C) is a characteristic diagram showing the MTF curve at the time of reduction,
FIG. 26 is a lens configuration diagram showing the basic configuration of a zoom lens for a variable magnification copying machine according to the invention of claims 3 and 4, and FIGS. Each of C) is a diagram for explaining the seventh embodiment of the present invention. Of these, Fig. 27 (A) is a lens configuration diagram when magnifying, Fig. 27 (B) is a lens configuration diagram when magnifying 1, and Fig. 27 (C) is a lens configuration diagram when reducing. Figure 28 (A1), (A2). (A3) is an aberration diagram showing spherical aberration, astigmatism, and distortion during magnification, No. 28 (Bl) (B2)
and (B3) are aberration diagrams showing spherical aberration, astigmatism, and distortion at the same magnification, FIG. 28 (C1),
(C2) and (C3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, at the time of reduction, and Fig. 29 (A)
is an aberration diagram showing coma aberration during magnification, FIG. 29 (
B) is an aberration diagram showing coma aberration at the same magnification, No. 29
Figure (C) is an aberration diagram showing coma aberration during reduction, and each of Figures 30 (A) to (C) to 32 (A) to (C) describes the eighth embodiment of the present invention. Figure 30 (A) is a diagram of the lens configuration when magnified, Figure 30 (B) is a diagram of the lens configuration when magnified to 1, and Figure 30 (C) is the diagram when reduced. Lens configuration diagram in
Figures 31 (A1), (A2), and (A3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, during magnification; Figures 31 (B1), (B2), and (B3) are Aberration diagrams showing spherical aberration, astigmatism, and distortion at the same magnification, and Figures 31 (cl), (C2), and (C3) show aberrations showing the spherical aberration, astigmatism, and distortion, respectively, at reduction. 32(A) is an aberration diagram showing comatic aberration when magnified, FIG. 32(B) is an aberration diagram showing comatic aberration when magnified, and FIG. 32(C) is an aberration diagram showing comatic aberration when magnified. Each of the aberration diagrams showing coma aberration, FIGS. 33(A) to 33(C) to FIG. 35(A) to (C), is a diagram for explaining the ninth embodiment of the present invention, and among these, Figure 33 (A)
is a lens configuration diagram at the time of magnification, and FIG. 33(B) is,
The lens configuration diagram at the same magnification, Figure 33 (C) is the lens configuration diagram at the time of reduction, Figure 34 (A1), (A2)
. (A3) is spherical aberration and astigmatism during magnification. Aberration diagrams showing distortion aberration, FIG. 34 (B1) (B
2), (B3) are aberration diagrams showing respectively spherical aberration, astigmatism, and distortion at the same magnification, FIG. 34 (C1),
(C2) and (C3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, at the time of reduction, and Fig. 35 (A)
is an aberration diagram showing comatic aberration during magnification, and Fig. 35 (
B) is an aberration diagram showing coma aberration at the same magnification, No. 35
Figure (C) is an aberration diagram showing coma aberration at the time of reduction, and each of Figures 36 (A) to (C) to 38 (A) to (C) describes the tenth embodiment of the present invention. Figure 36 (A) is a lens configuration diagram when magnified, Figure 36 (B) is a lens configuration diagram when the magnification is the same, and Figure 36 (C) is the lens configuration diagram when reduced. 37 (A1), (A2), and (A3) show spherical aberration during magnification. Aberration diagram showing astigmatism and distortion, Fig. 37 (
B1), (B2), and (B3) are aberration diagrams showing spherical aberration, astigmatism, and distortion at the same magnification, No. 37
Figures (C1), (C2), and (C3) are aberration diagrams showing spherical aberration, astigmatism, and distortion at the time of reduction, respectively, and Figure 38 (A) is an aberration diagram showing coma aberration at the time of expansion, Figure 38. (B) is an aberration diagram showing coma aberration at 1 magnification, 3rd
Figure 8 (C) is an aberration diagram showing coma aberration during reduction;
Figures 39 (A) to (C) to 4th engineering drawings (A) to (C)
39A and 39B are diagrams for explaining the eleventh embodiment of the present invention, of which FIG. 39(A) is a lens configuration diagram at the time of magnification, and FIG. 39(B) is a lens configuration diagram at the time of 2 equal magnification. The configuration diagram, FIG. 39 (C) is a lens configuration diagram at the time of reduction, and FIGS. 40 (A1), (A2), and (A3) are aberrations showing spherical aberration, astigmatism, and distortion aberration, respectively, at the time of expansion. Figures 40 (B1), (B2), and (B3) are aberration diagrams showing spherical aberration, astigmatism, and distortion, respectively, at the same magnification, and Figures 40 (C1), (C2), and (C3). teeth,
An aberration diagram showing spherical aberration, astigmatism, and distortion at the time of reduction, FIG. 41 (A) is an aberration diagram showing coma aberration at the time of enlargement, and FIG. 41 (B) is an aberration diagram showing the coma aberration at the same magnification. 41(C) is an aberration diagram showing comatic aberration during reduction, and each of FIGS. 42(A) to 44(A) to 44(E) are FIG. 42 (A) is a lens configuration diagram when magnified by 2.8 times, and FIG. 42 (B) is a diagram for explaining the 12th embodiment of the invention. FIG. 42 (C) is a lens configuration diagram at the same magnification.
Fig. 42 (I)) is a lens configuration diagram when reduced by 0.5 times, Fig. 42 (E) is a lens configuration diagram when reduced by 0.36 times, and Figs. 43 (A1) and (A2). (A3)
are aberration diagrams showing spherical aberration, astigmatism, and distortion at 2.8 times magnification, FIG. 43 (Bl),
(B2) and (B3) are aberration diagrams showing spherical aberration, astigmatism, and distortion at 2.0x magnification, and Figures 43 (C1), (C2), and (C3) are at 1x magnification. Aberration diagrams (Dl), (D2), and (D3) respectively showing spherical aberration, astigmatism, and distortion at 0.
Aberration diagrams showing spherical aberration, astigmatism, and distortion at the time of 5 times reduction, Fig. 43 (El), (1 mi 2),
(B3) is an aberration diagram showing spherical aberration, astigmatism, and distortion when reduced by 0.36 times, and Fig. 44 (A)
is an aberration diagram showing coma aberration at 2.8x magnification,
FIG. 44(B) is an aberration diagram showing comatic aberration when magnified by 2°0 times, FIG. 44(C) is an aberration diagram showing comatic aberration when magnified at 1x, and FIG. 44(D) is FIG. 14 (E) is an aberration diagram showing coma aberration when reduced by 0.5 times. FIG. 14 (E) is an aberration diagram showing coma aberration when reduced by 0.36 times. 1 to 3...surface, d1 to d12...axial spacing, Ll...first lens, B2...second lens. L3...Third lens, B4...Fourth lens, B5...Fifth lens, B6...Sixth lens, a...Aperture.

Claims (1)

[Scope of Claims] (1) In order from the object plane to the image plane, a first lens made of a concave lens with a concave surface facing the object side, a second lens made of a convex lens, and a meniscus with a concave surface facing the object side. a third lens made of a concave lens, an aperture, a fourth lens made of the same lens as the third lens and having a concave surface facing the image plane side, a fifth lens made of the same lens as the second lens; A zoom lens for a variable magnification copying machine with a configuration of 6 elements in 6 groups, which includes a 6th lens that is the same as the 1st lens and has a concave surface facing the image plane side, and the object plane is the same magnification as the image plane. When forming an image on the image plane, the first to sixth lenses are arranged symmetrically about the diaphragm, and when the object plane is magnified and imaged on the image plane, at least the first lens and the sixth lens are arranged symmetrically with respect to the aperture. 6 lenses are used as a fixed group, and at least the second lens and the fifth lens of the diaphragm are moved asymmetrically, and the entire lens system is moved in the optical axis direction. A zoom lens for a variable magnification copying machine, characterized in that the conjugate length to the image plane is kept constant regardless of whether the magnification is equal or variable, and continuous magnification is possible. (2) When the focal length of the first lens is f1, the focal length of the third lens is f3, and the composite focal length of the entire lens system at equal magnification is f0, 0.4<|f1/f0| 2. The zoom lens for a variable magnification copying machine according to claim 1, wherein the zoom lens satisfies the following conditions: <0.65 and 0.7<|f3/f0|<1.4. (3) In order from the object plane to the image plane, the first lens is a concave lens with a concave surface facing the object side, the second lens is a convex lens, and the third lens is a meniscus concave lens with a concave surface facing the object side. , an aperture, a fourth lens made of the same lens as the third lens and having a concave surface facing the image plane side, a fifth lens made of the same lens as the second lens, and a fifth lens the same as the first lens. A zoom lens for a variable magnification copying machine with a configuration of 6 elements in 6 groups and a 6th lens with a concave surface facing the image plane side. , the first to sixth lenses are arranged symmetrically about the aperture, and when the object plane is magnified and imaged on the image plane, the first lens, the third lens, and the fourth lens and the sixth lens as a fixed group, and by moving the second and fifth lenses asymmetrically and moving the entire lens system in the optical axis direction, the conjugate length from the object plane to the image plane can be adjusted at the same magnification. A zoom lens for a variable magnification copying machine, which is characterized by being able to continuously change the magnification while keeping the magnification constant regardless of when the magnification is changed. (4) When the focal length of the first lens is f1, the focal length of the second lens is f2, and the composite focal length of the entire lens system at equal magnification is f0, 0.4<|f1/f0| 4. The zoom lens for a variable magnification copying machine according to claim 3, wherein the zoom lens satisfies the following conditions: <0.7 and 0.3<f2/f0<0.45.