JPH05142471A - Magnifying and reducing lens - Google Patents

Abstract

PURPOSE:To realize the novel magnifying and reducing lens which is low in cost and squall in curvature of image. CONSTITUTION:This lens is constituted by arranging 1st-3rd groups from the magnification side to the reduction side. The 1st group 11 is a positive meniscus lens 11 which is convex to the magnification side, the 2nd group 12 is a biconcave lens, and the 3rd group 13 is a biconvex lens; and the lens consists of the three elements in the three groups. Then, an inequality I 0.34<¦f2/f¦<0.4, an inequality II 0.21<SIGMA<d/f<0.4, and an equation III 0.3<r1/f<0.34 are satisfied, where f is the composite focal length of the whole system, f2 the focal length of the 2nd group, SIGMAd the lens overall length, and r1 the radius of curvature of the 1st lens surface counted from the magnification side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnification / reduction lens. INDUSTRIAL APPLICABILITY The present invention can be used as a magnifying projection lens for an overhead projector or a microfilm reader, or as a microfilm photographing lens.

[0002]

2. Description of the Related Art Magnifying lenses have been widely known in the past in relation to overhead projectors and microfilm readers (for example, Japanese Patent Publications No. 54-8302, No. 57-13848, and Japanese Unexamined Patent Publication No. 60-4668).
7 and 61-52618).

Each of these conventional magnifying lenses is designed as a combination of five or more lenses, and there is a problem that the number of constituent lenses is large and the cost is high.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to magnify and project a 35 mm film or a liquid crystal display at a magnification of 5 or 10 times, or 1/5. Alternatively, it is an object of the present invention to provide a novel enlargement / reduction lens which is suitable for microfilm photography at a reduction ratio of about 1/10, can be realized at low cost, and has a small field curvature.

[0005]

As shown in FIG. 1, a magnifying / reducing lens of the present invention is a magnifying side (left side in the figure, an image side at a magnifying power, and an object side at a reducing magnifying power). ) From the reduction side (to the right in the figure, the object side at the enlargement magnification, and the image side at the reduction magnification).
It is composed by arranging groups.

The first group 11 is a positive meniscus lens having a convex surface facing the magnification side, the second group 12 is a biconcave lens, and the third group 13 is
Is a biconvex lens, and is composed of 3 elements in 3 groups.

When the synthetic focal length of the entire system is f, the focal length of the _second lens group 12 is f ₂ , the total lens length is Σd, and the radius of curvature of the _first lens surface counted from the enlargement side is r _1. 1
In the scaling lens, they condition _{(1-1) 0.34 <| f 2} /f|<0.4 (1-2) 0.21 <Σd / f <0.4 (1-3) It satisfies 0.3 <r ₁ /f<0.34. The magnifying / reducing lens according to claim 1 is suitable for use at a magnifying power of about 10 times and at a demagnifying power of about 1/10, and is particularly suitable for use as a magnifying lens at a magnifying power of about 10 times.

Further, in the magnifying / reducing lens according to claim 2,
The above f, f ₂ , Σd, and r ₁ satisfy the condition (2-1) 0.3 <| f ₂ /f|<0.34 (2-2) 0.15 <Σd / f <0.25 (2 -3) 0.22 <r ₁ /f<0.29 is satisfied. The magnifying / reducing lens of claim 2 is suitable for use at a magnifying power of about 5 times and at a demagnifying power of about 1/5, and is particularly suitable for use as a magnifying lens at a magnifying power of about 5 times.

[0009]

As described above, the magnifying / reducing lenses according to the first and second aspects have the same lens structure, but have different use magnifications. Each condition is a condition for achieving good performance at each use magnification.

The conditions (1-1) and (2-1) are the ranges of the refractive power of the second lens group suitable for realizing a wide angle of view and a large aperture in the lenses of claims 1 and 2, respectively. When the upper limits are exceeded, the Petzval sum becomes large, the image surface tilts in the negative direction, and astigmatism becomes large. If the lower limit of each conditional expression is exceeded, the Petzval sum will become small, the image plane will tilt in the positive direction, and the field curvature will become large. Therefore, outside the range of each conditional expression, the axial and off-axis aberration balance cannot be maintained and a wide angle of view cannot be realized.

The conditions (1-2) and (2-2) are conditions for making the lens system compact. When the upper limits of the respective conditions are exceeded, the total lens length becomes too large and the lens effective diameter also becomes large so that the lens system becomes compact. Can not. When the value goes below the lower limit, it is advantageous for downsizing, but the coma flare increases and it is impossible to realize a large aperture.

The conditions (1-3) and (2-3) are the lens on the most magnifying side when an appropriate refracting power is given to the second lens group by the above conditional expressions (1-1) and (2-1). It shows an appropriate range of the radius of curvature of the surface. When the upper limit of each is exceeded, the positive power becomes insufficient, the spherical aberration becomes positive, and the coma flare becomes too large. If the respective lower limits are exceeded, astigmatism and distortion will deteriorate.

In the enlarging / reducing lens of the first aspect, by satisfying the conditions (1-1), (1-2) and (1-3), F / No: about 5 is bright, and the half angle of view is about 30 degrees. And a wide-angle lens can be realized. In the enlarging / reducing lens according to claim 2, by satisfying the conditions (2-1), (2-2) and (2-3), the brightness is about F / No: 7 and the half angle of view is about 30.
A wide-angle lens with a high degree can be realized.

[0014]

[Examples] Six specific examples will be given below. Examples 1 to 3 are examples relating to the enlargement / reduction lens of claim 1,
Examples 4 to 6 are examples of the magnifying / reducing lens according to claim 2, and are all cases in which the magnifying power is used. Further, as shown in FIG. 1, a diaphragm is arranged between the second and third groups.

In each embodiment, as shown in FIG. 1, the radius of curvature of the i-th lens surface counted from the enlargement side is r _i (i =
1 to 6), the surface distance between the i-th lens surface and the (i + 1) th lens surface on the optical axis is d _i (i = 1 to 5), counted from the enlargement side to the j-th
The refractive index and Abbe number of the th lens are
It is represented by n _j and ν _j (j = 1 to 3). Further, F / No is brightness, ω is a half angle of view (unit: degree), m is a magnification, f is a combined focal length of the entire system, f ₂ is a focal length of the second group, and Σd is a total lens length.

Example 1 f = 30.36, F / No = 4.98, m = 10.76, ω = 31.4 f ₂ = -11.92, Σd = 8.74 i r _i d _i j n _j ν _j 1 9.478 2.71 1 1.8040 46.6 2 18.071 0.68 3 41.397 1.50 2 1.6727 32.1 4 10.094 0.87 5 22. 864 2.98 3 1.7725 49.6 6-23.780.

Parameter values for each condition | f ₂ /f|=0.39, Σd / f = 0.29, r ₁ / f
= 0.31.

Example 2 f = 30.36, F / No = 5.27, m = 10.76, ω = 31.4 f ₂ = -11.95, Σd = 11.53 i r _i d _i j n _j ν _j 1 10.252 3.25 1 1.8830 40.8 2 18.221 0.56 3 -66.173 1.70 2 1.7182 26.6 4 10.670 0.69 5 22. 499 5.33 3 1.8830 40.8 6 -30.555.

Parameter values of each condition: | f ₂ /f|=0.39, Σd / f = 0.38, r ₁ / f
= 0.34.

Example 3 f = 30.36, F / No = 5.27, m = 10.76, ω = 31.4 f ₂ = -10.95, Σd = 7.2 i r _i d _i j n _j ν _j 1 9.275 2.61 1 1.7130 53.9 2 15.849 0.94 3 -21.035 1.50 2 1.6727 32.1 4 11.660 0.59 5 23. 016 5.33 3 1.8348 42.7 6-18.095.

Parameter value of each condition | f ₂ /f|=0.36, Σd / f = 0.24, r ₁ / f
= 0.31.

Example 4 f = 68.37, F / No = 7.00, m = 4.42, ω = 31.5 f ₂ = -21.62, Σd = 10.97 i r _i d _i j n _j ν _j 1 16.250 4.56 1 1.6760 57.4 2 27.178 1.10 3 -35.900 1.50 2 1.5814 40.8 4 19.637 1.40 5 43. 037 2.41 3 1.6700 57.4 6-28.728.

Parameter value of each condition | f ₂ /f|=0.32, Σd / f = 0.16, r ₁ / f
= 0.24.

Example 5 f = 68.37, F / No = 7.00, m = 4.42, ω = 31.5 f ₂ = −22.65, Σd = 12.69 i r _i d _i j n _j ν _j 1 17.298 5.00 1 1.7550 52.3 2 28.985 0.93 3 −46.959 1.50 2 1.6034 38.0 4 19.515 1.57 5 45. 247 3.69 3 1.6700 57.4 6-32.658.

Parameter value of each condition | f ₂ /f|=0.33, Σd / f = 0.19, r ₁ / f
= 0.25.

Example 6 f = 68.37, F / No = 7.00, m = 4.42, ω = 31.5 f ₂ = −22.33, Σd = 15.76 i r _i d _i j n _j ν _j 1 19.112 5.26 1 1.7292 54.7 2 26.444 1.58 3 −46.428 5.38 2 1.6889 31.1 4 24.089 0.65 5 35. 511 2.89 3 1.8830 40.8 6-47.044.

Parameter value of each condition | f ₂ /f|=0.33, Σd / f = 0.23, r ₁ / f
= 0.28.

FIGS. 2 to 7 sequentially show aberration diagrams of Examples 1 to 6. Symbols in each aberration diagram: 1 is d line, 2 is g
Line 3 represents the C line, respectively. Y means the image height at the magnification. The broken line in the diagram of spherical aberration represents the sine condition, the solid line in the diagram of astigmatism represents the radial direction, and the broken line represents the tangential direction. In each of the examples, various aberrations are corrected well, and the performance is good.

[0029]

As described above, according to the present invention, a novel enlargement / reduction lens can be provided. As described above, this lens can be realized at a low price because it has a three-element configuration and a small number of elements, and is lightweight, compact, and has good performance.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a lens configuration of a magnifying / reducing lens of the present invention.

FIG. 2 is an aberration diagram for Example 1.

FIG. 3 is an aberration diagram for Example 2.

FIG. 4 is an aberration diagram for Example 3.

FIG. 5 is an aberration diagram for Example 4.

FIG. 6 is an aberration diagram for Example 5.

FIG. 7 is an aberration diagram for Example 6.

[Explanation of symbols]

11 First Group 12 Second Group 13
Third group

Claims (4)

[Claims] 1. A first meniscus lens having a convex surface facing the enlargement side, a second group consisting of a biconcave lens, and a first to a third lens group arranged in order from the enlargement side to the reduction side. The third lens group is a biconvex lens with three lens groups and three lenses. The total focal length of the entire system is f, the focal length of the _second lens group is f ₂ , the total lens length is Σd, and the first lens surface is counted from the magnification side. When the radius of curvature of r is r ₁ , these are conditions (1-1) 0.34 <| f ₂ /f|<0.4 (1-2) 0.21 <Σd / f <0.4 (1 -3) A magnifying / reducing lens characterized by satisfying 0.3 <r ₁ /f<0.34. 2. A first meniscus lens having a convex surface directed toward the enlargement side, a second group consisting of a biconcave lens, and a first group consisting of first to third groups arranged in order from the enlargement side toward the reduction side. The third lens group is a biconvex lens composed of three lenses in three groups. The total focal length of the entire system is f, the focal length of the _second lens group is f ₂ , the total lens length is Σd, and the first lens surface is counted from the magnification side. When the radius of curvature of r is r ₁ , these conditions (2-1) 0.3 <| f ₂ /f|<0.34 (2-2) 0.15 <Σd / f <0.25 (2 -3) A magnifying / reducing lens characterized by satisfying 0.22 <r ₁ /f<0.29. 3. The magnifying / reducing lens according to claim 1, which is used at a magnifying power of about 10 times. 4. The magnifying / reducing lens according to claim 2, which is used at a magnifying power of about 5 times.