JP3332677B2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens and, more particularly, to a zoom lens for projection in which magnification is changed while maintaining a constant finite distance between object images suitable for a microfilm reader printer or the like. is there.

[0002]

2. Description of the Related Art Conventionally, in a projection optical system such as a microfilm reader printer or the like, a zoom for projection in which a variable magnification is performed and a projection magnification is continuously obtained while maintaining a constant finite distance between object images. Various lenses have been proposed. This zoom lens is characterized in that the projection magnification can be obtained continuously and quickly and easily as compared with a turret type in which a plurality of fixed focus lenses are rotated.

For example, Japanese Patent Application Laid-Open Nos. 62-280814 and 2-105211 disclose a first group of negative refractive power and a second group of positive refractive power in order from the screen side (enlargement side).
A so-called two-group type zoom lens for projection having two lens groups, maintaining the object-image distance at a constant finite distance, and changing the distance between the two lens groups to perform zooming is disclosed. .

In general, a zoom lens used in a projection optical system such as a microfilm reader printer has a rotatable image rotating prism (rotation prism) disposed at an exit of a zoom lens on a screen (magnification) side to form a predetermined projected image. The image is selectively projected on the screen surface and the photosensitive drum surface while being rotated by an angle.

A zoom lens combined with this image rotation prism has been proposed in, for example, Japanese Patent Application Laid-Open Nos. 4-195111 and 5-341186.

[0006]

In a microreader, a reader printer, or the like, a rotatable image rotation prism (rotation prism) is arranged on a screen side (enlargement side) of a zoom lens to rotate a projected image by a required angle. Then, the vertical and horizontal positions are corrected.

For this reason, if the pupil on the screen side of the zoom lens is located at a reduced side position distant from the first lens surface when counted from the screen surface, a large-sized pupil is required to prevent vignetting of light beams at four corners on the screen. It is necessary to use a rotation prism, which results in an increase in the size of the entire apparatus and deterioration of optical performance. For this reason, the pupil on the screen side is configured to be located near the first lens surface of the zoom lens, thereby reducing the size of the rotation prism.

However, in such a lens configuration, if an attempt is made to obtain a high zoom ratio, the variation in aberrations, particularly the variation in curvature of field, associated with zooming becomes large, and a complicated zoom configuration is required to correct this. And the zoom lens as a whole becomes larger.

According to the present invention, by appropriately setting the lens configuration of each lens unit of the two-unit zoom lens, the pupil position on the screen side is made closer to the first lens surface, and a small rotation prism can be used. It is an object of the present invention to provide a zoom lens having high optical performance over the entire zoom range while securing a high zoom ratio of about 2.5.

[0010]

According to the present invention, there is provided a zoom lens comprising: (1) a first lens unit having a negative refractive power and a second lens unit having a positive refractive power in order from a magnification side; The zooming from the end to the telephoto end is performed by moving the first unit with a convex locus on the reduction side and moving the second unit monotonously to the enlargement side. Comprises a negative first lens having a concave surface, a negative meniscus lens having a convex surface directed to the reduction side, and a third positive lens having a convex surface directed to the enlargement side. A positive fourth lens having a convex surface, a meniscus-shaped positive fifth lens having a convex surface facing the enlargement side, a negative sixth lens, a meniscus-shaped positive seventh lens having a convex surface facing the enlargement side, and the enlargement side A negative meniscus lens having a convex surface facing the positive lens, a positive ninth lens having both lens surfaces convex, and a negative negative lens having both lens surfaces concave. A bonded first lens in which three lenses of a tenth lens are cemented, and a positive eleventh lens having both lens surfaces convex.
Lens, positive twelfth with convex surface of strong refractive power facing the reduction side
Lens, positive thirteenth with convex surface with strong refractive power facing magnifying side
It is characterized in that it comprises a cemented second lens in which a lens and a negative fourteenth lens whose both lens surfaces are concave are joined, and a negative fifteenth lens having a concave surface having a strong refractive power directed to the enlargement side.

(2) The first lens unit includes a first lens unit having a negative refractive power and a second lens unit having a positive refractive power in order from the magnification side. The first lens unit changes the magnification from the wide-angle end to the telephoto end. Is moved by having a convex locus on the reduction side, and the second group is moved monotonously to the enlargement side. The first group is a negative first lens having both concave lens surfaces and a convex surface on the reduction side. A second meniscus negative lens having a positive surface, and a positive third lens having a convex surface facing the enlargement side. The second group is composed of an aperture, a fourth positive lens having both lens surfaces convex, and a fourth lens having a convex surface. Meniscus positive fifth lens with a convex surface facing the lens, negative sixth lens, meniscus positive seventh lens with a convex surface facing the magnification side, and meniscus negative eighth lens with a convex surface facing the magnification side And three lenses, a positive ninth lens with both lens surfaces convex and a negative tenth lens with both lens surfaces concave A first lens, a positive eleventh lens with both lens surfaces being convex, a cemented second lens in which a negative twelfth lens is cemented with a positive thirteenth lens with both lens surfaces convex, with the convex surface facing the enlargement side It is characterized by comprising a positive meniscus fourteenth lens and a negative fifteenth lens having a concave surface having a strong refractive power directed to the enlargement side.

[0012]

1 to 3 are lens sectional views of Numerical Examples 1 to 3 of the present invention. In the figure, L1 is a first group having a negative refractive power, L2 is a second group having a positive refractive power, and has two lens groups, a front group L2a and a rear group L2b. Arrows indicate the moving direction of each lens group when zooming from the short focal end (wide-angle end) to the long focal end (telephoto end). The first group L1 side is an enlargement side (screen side), and the second group L2 side is a reduction side. G is a holding plate glass such as a microfilm when used as a projection system.

FI is an object to be projected such as a microfilm,
SP denotes an aperture, which moves integrally with the second lens unit. In this embodiment, the enlargement side is defined as an object point and an image point at an arbitrary zoom position.
When two conjugate points are taken, it is the side where the conjugate point farther from the principal point of the zoom lens exists. The reduction side is the opposite side.

4 to 6 are aberration diagrams of Numerical Embodiments 1 to 3 of the present invention. In the aberration diagrams, (A) is at the wide-angle end (high magnification), (B) is at the telephoto end (low magnification), and has a thickness 69.82 corresponding to an image inverting prism on the enlargement side, n = 1.744, ν.
This shows the aberration when a glass of = 44.8 is arranged.

In this embodiment, as shown in FIGS. 1 to 3, upon zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves from the enlargement side to the reduction side, and on the way to the enlargement side via the inflection point. Move,
That is, the second lens unit moves while having a convex locus on the reduction side, and the second group moves monotonously from the reduction side to the enlargement side.

In this embodiment, the first group having a negative refractive power on the enlargement side is constituted by three lenses having a predetermined shape, and the second group having a positive refractive power on the reduction side is constituted by twelve lenses having a predetermined shape. While maintaining the object-image distance at a constant finite distance,
By moving the group while having a convex locus on the reduction side and moving the second group monotonously to the enlargement side, zooming from the short focal end (wide-angle end) to the long focal end (telephoto end) is performed. The projection magnification on the screen side is continuously changed within the range of -50 to -20.

As a result, a zoom lens having a high resolving power with little variation in aberration during zooming over the entire screen at various projection magnifications is obtained. The pupil is positioned near the first lens surface on the enlargement side to reduce the size of the image rotation prism when used in a microreader or the like.

Particularly, in this embodiment, the zoom lens is composed of two lens units, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, and a stop is arranged immediately before the second unit to change the magnification. Is moved together with the second group. Thereby, the movement of the pupil on the enlargement side is suppressed as much as possible, and the outer diameter of the lens of the second group is suppressed, so that good imaging performance can be easily obtained.

Next, the features of the lens configuration of each lens unit of this embodiment will be described. First, the lens configurations of Numerical Examples 1 and 2 in FIGS. 1 and 2 will be described. In FIGS. 1 and 2, the first lens unit having a negative refractive power more strongly on the reduction side than on the enlargement side (meaning in comparison with the enlargement side; the same applies hereinafter). A negative meniscus second lens having a convex surface facing the reduction side at a predetermined distance from the lens, and a positive third lens having a strong convex surface facing the enlargement side.

By forming a negative air lens between the first lens and the second lens, the occurrence of coma is suppressed,
In addition, since the second lens has a meniscus shape, occurrence of astigmatic difference is suppressed. The second group having a positive refractive power is divided into a front group L2a from the fourth lens to the seventh lens and a rear group L2b from the eighth lens to the fifteenth lens, and the front group L2a and the rear group L2b are separated at a relatively wide interval. The lens configuration is separated.

The front group L2a of the second group has a lens shape which is mainly useful for correcting spherical aberration on the high magnification side where the F number is bright. In particular, the fifth lens and the sixth lens constitute an air lens to correct spherical aberration. By forming the seventh lens in a meniscus shape with the convex surface facing the enlargement side, the occurrence of coma is suppressed. By setting a certain distance between the seventh lens and the eighth lens, the roles of correcting the on-axis aberration and the off-axis aberration can be shared. This makes it easy to correct mainly the spherical aberration on the high magnification side in the front group and the off-axis aberration on the low magnification side in the rear group.

The first lens to be bonded is formed by joining three lenses of eighth, ninth, and tenth lenses having a predetermined shape, and at this time, forming a lens having two bonded lens surfaces having negative refractive power. The spherical aberration that cannot be completely corrected by the front group is corrected, and the field curvature is corrected.

The eleventh lens, the twelfth lens, and the first
The cemented second lens composed of the third lens and the fourteenth lens has a positive refractive power, has a role of gradually narrowing the light flux, and prevents coma aberration from being generated as much as possible. Further, the twelfth lens and the bonded second lens are arranged so as to oppose a strong convex surface, thereby correcting astigmatic difference. Thirteenth
The chromatic aberration of magnification is mainly corrected by the bonded second lens including the lens and the fourteenth lens.

The fifteenth lens forms an air lens with the fourteenth lens and plays a role of flattening the image surface. In addition, a certain amount of lens back is ensured, and a roll fish carrier or the like can be used. The second group is close to the film surface on the high magnification side, and it is necessary to secure a lens back. Since the effective screen area of the film is widened on the low magnification side, the aberration correction of the rear group is performed on the field curvature and coma on the low magnification side. As a result, a zoom lens having a high zoom ratio, in which a variation in curvature of field during zooming is small and good imaging performance is always obtained on the entire screen, is realized.

In the present invention, in order to further obtain high optical performance over the entire zoom range under such a lens shape, it is preferable to satisfy the following conditional expressions (1a) to (5a).

Considering the stop as one surface, counting from the enlargement side, the radius of curvature of the i-th lens surface is Ri, the i-th lens thickness or air gap is Di, and the refractive index of the material of the i-th lens is When the Abbe numbers are Ni and νi, the refractive power of the i-th lens is φi, and the focal length at the wide-angle end of the entire system is fw.

[0027]

(Equation 3) Satisfying the following conditions.

Next, a description will be given of a lens configuration of a numerical example 3 of FIG. The numerical embodiment 3 of FIG. 3 has exactly the same lens configuration and optical function as the first to eleventh lenses and the fifteenth lens as compared with the numerical embodiments 1 and 2 of FIGS.

The difference is that the twelfth lens has a negative refracting power, the thirteenth lens has a positive refracting power, the both are cemented second lenses, and the fourteenth lens has a meniscus having a convex surface facing the enlarged side. Is a positive refractive power in the shape of. The optical actions of the twelfth to fourteenth lenses are substantially the same as the optical actions of the twelfth to fourteenth lenses of Numerical Examples 1 and 2 in FIGS.

In the present invention, it is preferable to satisfy the following conditional expressions (1b) to (5b) in order to further obtain high optical performance over the entire zoom range under such a lens shape.

Considering the stop as one surface, counting from the enlargement side, the radius of curvature of the i-th lens surface is Ri, the i-th lens thickness or air gap is Di, and the refractive index of the material of the i-th lens is When the Abbe numbers are Ni and νi, the refractive powers of the eleventh lens and the laminated second lens are φ11 and φA, respectively, and the focal length at the wide-angle end of the entire system is fw.

[0032]

(Equation 4) Satisfying the following conditions.

Here, the conditional expressions (1a) to (5a) and the conditional expressions (1b) to (5b) correspond to each other. For example, both conditional expressions (2a) and (2b)
Regarding the Abbe number of the material of the positive lens and the negative lens of the lens,
Conditional expressions (5a) and (5b) both relate to the ratio of the refractive power of the two lenses behind the bonded first lens, and conditional expression (5a) relates to the ratio of the refractive powers of the two positive lenses. Equation (5b) relates to the ratio of the refractive power of one positive lens to the cemented second lens.

Next, the technical meaning of each of the above conditional expressions will be described. Conditional expressions (1a) and (1b) are conditions for correcting spherical aberration and field curvature on the high magnification side. When the value exceeds the upper limit, the influence of coma aberration becomes large. When the value exceeds the lower limit, the effect of correcting spherical aberration and correcting field curvature becomes weak.

The conditional expressions (2a) and (2b) are for correcting especially the chromatic aberration of magnification on the low magnification side. When the value exceeds the upper limit, the lateral chromatic aberration is overcorrected, and when the value exceeds the lower limit, the lateral chromatic aberration is undercorrected.

Conditional expressions (3a) and (3b) are used to share the role of aberration correction of the front unit L2a of the second unit to some extent.
The back focus becomes shorter and the dimensions are adversely affected. If the lower limit is exceeded, the function of sharing the aberrations of the front unit L2a and the rear unit L2b is weakened, and it is particularly difficult to balance the spherical aberration of the second lens unit and the aberration correction of the field curvature.

The conditional expressions (4a) and (4b) are for securing the back focal length on the high magnification side and for flattening the image surface. If the value exceeds the upper limit, coma aberration occurs and the performance deteriorates. If the lower limit value is exceeded, the back focal length on the high magnification side becomes short, making it difficult to insert a roll film carrier or the like, increasing the field curvature, and making it difficult to obtain good performance over the entire screen.

Conditional expressions (5a) and (5b) correspond to the second bonding
The purpose is to gradually narrow down the luminous flux diverged by the lens and to lead to image formation while maintaining good performance. If the value exceeds the upper limit, coma aberration occurs. If the value exceeds the lower limit, the lens length increases, which is not good.

Next, a case where the zoom lens of this embodiment is applied to a micro reader will be described with reference to FIG. In the figure,
Reference numeral 2 denotes a zoom lens according to the present invention, which enlarges and projects the microfilm F on a screen 7 via a rotation prism 3 and folding mirrors 4, 5, and 6.

The rotation prism 3 is rotatably disposed near the exit of the zoom lens 2 on the enlarged side.
By this rotation (rotation in the XZ plane in the drawing), the projected image is rotated by a required angle and emitted.

That is, when the top and bottom (vertical and horizontal positions) of the image information of the microfilm F are not correctly recorded, the projected image is rotated (rotated in the YZ plane in the drawing) so that the projected image can be easily observed. ing.

In this embodiment, the pupil position on the screen 7 side is located near the first lens surface, so that a relatively small rotation prism 3 can be used. Further, despite the fact that the projection magnification to the screen side is as high as -50 to -20, the zoom lens itself is also relatively small, so that the whole apparatus can be miniaturized.

Further, according to the present embodiment, not only the rotation prism but also the optical element on the enlargement side such as a mirror for switching the optical path with the reader printer when applied to the reader printer is miniaturized.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass. Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

<Numerical Example 1> f = 25.26 to 60.28 Fno = 1: 2.4 to 1: 6 Magnification -1/50 to -1/20 R 1 = -133.34 D 1 = 1.00 N 1 = 1.77250 ν 1 = 49.6 R 2 = 27.75 D 2 = 5.03 R 3 = -24.93 D 3 = 1.70 N 2 = 1.77250 ν 2 = 49.6 R 4 = -32.90 D 4 = 0.20 R 5 = 58.11 D 5 = 2.50 N 3 = 1.84666 ν 3 = 23.9 R 6 = 726.15 D 6 = Variable R 7 = ∞ (Aperture) D 7 = 0.30 R 8 = 48.85 D 8 = 3.50 N 4 = 1.77250 ν 4 = 49.6 R 9 = -132.01 D 9 = 0.20 R10 = 36.62 D10 = 4.00 N 5 = 1.69680 ν 5 = 55.5 R11 = 179.84 D11 = 0.95 R12 = -95.90 D12 = 1.50 N 6 = 1.80518 ν 6 = 25.4 R13 = 1989.74 D13 = 2.21 R14 = 29.48 D14 = 4.50 N 7 = 1.51633 ν 7 = 64.2 R15 = 40.65 D15 = 5.50 R16 = 52.11 D16 = 1.04 N 8 = 1.84666 ν 8 = 23.9 R17 = 15.26 D17 = 7.23 N 9 = 1.48749 ν 9 = 70.2 R18 = -17.50 D18 = 0.99 N10 = 1.83400 ν10 = 37.2 R19 = 54.41 D19 = 0.56 R20 = 28.58 D20 = 3.50 N11 = 1.69680 ν11 = 55.5 R21 = -55.53 D21 = 1.50 R22 = 754.39 D22 = 3.00 N12 = 1.62004 ν12 = 36.3 R23 = -31.92 D23 = 0.08 R24 = 39.51 D24 = 3.65 N13 = 1.80518 ν13 = 25.4 R25 = -32.35 D25 = 1.00 N14 = 1.77250 ν14 = 49.6 R26 = 49.30 D26 = 3.61 R27 = -15.77 D27 = 1.50 N15 = 1.71300 ν15 = 53.8 R28 = -216.97 D28 = Variable R29 = ∞ D29 = 3.00 N16 = 1.51633 ν16 = 64.2 R30 = ∞ (Film surface) R1 to R6; First lens group R8 to R28; Second lens group R29, R30; holding plate glass Distance between objects 1360 (converted to prism air) ＼focal length 25.26 60.28 43.19 variable interval＼ D6 25.55 1.58 8.43 D28 9.49 33.46 21.47 <Numerical example 2> f = 25.26 to 60.28 Fno = 1: 2.4 to 1: 6 Magnification -1/50 to -1/20 R 1 = -122.38 D 1 = 1.00 N 1 = 1.77250 ν 1 = 49.6 R 2 = 26.77 D 2 = 4.53 R 3 = -26.40 D 3 = 1.70 N 2 = 1.77250 ν 2 = 49.6 R 4 = -34.47 D 4 = 0.20 R 5 = 51.26 D 5 = 2.50 N 3 = 1.84666 ν 3 = 23.9 R 6 = 363.48 D 6 = Variable R 7 = ∞ (aperture) D 7 = 0.30 R 8 = 52.71 D 8 = 3.00 N 4 = 1.77250 ν 4 = 49.6 R 9 = -133.83 D 9 = 0.20 R10 = 38.02 D10 = 3.00 N 5 = 1.69680 ν 5 = 55.5 R11 = 232.97 D11 = 0.76 R12 = -112.73 D12 = 1.50 N 6 = 1.80518 ν 6 = 25.4 R13 = 327.58 D13 = 0.13 R14 = 28.99 D14 = 4.85 N 7 = 1.51633 ν 7 = 64.2 R15 = 39.82 D15 = 7.55 R16 = 50.59 D16 = 1.10 N 8 = 1.84666 ν 8 = 23.9 R17 = 15.85 D17 = 8.41 N 9 = 1.48749 ν 9 = 70.2 R18 = -17.20 D18 = 1.00 N10 = 1.83481 ν10 = 42.7 R19 = 77.31 D19 = 0.45 R20 = 26.04 D20 = 4.60 N11 = 1.55963 ν11 = 61.2 R21 = -32.60 D21 = 0.48 R22 = -832.63 D22 = 2.70 N12 = 1.69895 ν12 = 30.1 R23 = -52.76 D23 = 0.20 R24 = 39.10 D24 = 3.42 N13 = 1.75520 ν13 = 27.5 R25 = -42.35 D25 = 1.00 N14 = 1.80400 ν14 = 46.6 R26 = 74.27 D26 = 4.86 R27 = -14.95 D27 = 1.00 N15 = 1.51633 ν15 = 64.2 R28 = 104.70 D28 = Variable R29 = ∞ D29 = 3.00 N16 = 1.51633 ν16 = 64.2 R30 = ∞ (Film Surface) R1 to R6; first lens group R8 to R28; second lens group R29, R30; holding plate glass Distance between objects 1360 (in terms of prismatic air) ＼focal length 25.26 60.28 43.19 variable interval＼ D6 25.52 1.55 8.40 D28 9.50 33.47 21.48 <Numerical Example 3> f = 25.26 to 60.28 Fno = 1: 2.4 to 1: 6 Magnification -1/50 to -1/20 R 1 = -119.94 D 1 = 1.00 N 1 = 1.77250 ν 1 = 49.6 R 2 = 27.22 D 2 = 4.67 R 3 = -26.29 D 3 = 1.70 N 2 = 1.77250 ν 2 = 49.6 R 4 = -35.46 D 4 = 0.20 R 5 = 56.52 D 5 = 2.50 N 3 = 1.84666 ν 3 = 23.9 R 6 = 2167.84 D 6 = Variable R 7 = ∞ (aperture) D 7 = 0.30 R 8 = 53.41 D 8 = 3.00 N 4 = 1.77250 ν 4 = 49.6 R 9 = -131.51 D 9 = 0.20 R10 = 36.16 D10 = 3.00 N 5 = 1.69680 ν 5 = 55.5 R11 = 259.60 D11 = 0.75 R12 = -108.61 D12 = 1.50 N 6 = 1.80518 ν 6 = 25.4 R13 = 397.23 D13 = 0.20 R14 = 29.32 D14 = 5.37 N 7 = 1.51633 ν 7 = 64.2 R15 = 37.57 D15 = 5.47 R16 = 53.24 D16 = 1.10 N 8 = 1.84666 ν 8 = 23.9 R17 = 15.70 D17 = 9.07 N 9 = 1.48749 ν 9 = 70.2 R18 = -18.22 D18 = 1.00 N10 = 1.83481 ν10 = 42.7 R19 = 82.74 D19 = 0.44 R20 = 26.20 D20 = 4.20 N11 = 1.51633 ν11 = 64.2 R21 = -36.39 D21 = 0.20 R22 = -209.97 D22 = 1.00 N12 = 1.69680 ν12 = 55.5 R23 = 64.97 D23 = 2.97 N13 = 1.75520 ν13 = 27.5 R24 = -44.20 D24 = 0.29 R25 = 41.12 D25 = 2.50 N14 = 1.75520 ν14 = 27.5 R26 = 81.67 D26 = 6.50 R27 = -15.64 D27 = 1.00 N15 = 1.58913 ν15 = 61.2 R28 = 272.81 D28 = Variable R29 = ∞ D29 = 3.00 N16 = 1.51633 ν16 = 64.2 R30 = ∞ (Film surface) R1 to R6; First lens group R8 to R28; Second lens group R 29, R30; holding plate glass Distance between objects 1360 (converted to prismatic air) ＼focal length 25.26 60.28 43.19 variable interval＼ D 6 25.49 1.52 8.36 D28 9.51 33.48 21.50

[0046]

[Table 1]

[0047]

According to the present invention, as described above, the pupil position on the screen side is brought closer to the first lens surface by appropriately setting the lens configuration of each lens unit of the two-unit zoom lens, and a small rotation is achieved. Enables the use of prisms,
A zoom lens having high optical performance over the entire zoom range can be achieved while securing a high zoom ratio of about 2.5.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a lens at a wide-angle end according to a second numerical embodiment of the present invention.

FIG. 3 is a sectional view of a lens at a wide-angle end according to a third numerical embodiment of the present invention;

FIG. 4 is an aberration diagram of a numerical example 1 of the present invention.

FIG. 5 is an aberration diagram of Numerical Example 2 of the present invention.

FIG. 6 is an aberration diagram of a numerical example 3 of the present invention.

FIG. 7 is an explanatory diagram when the zoom lens of the present invention is applied to a micro reader.

[Explanation of symbols]

 L1 First group L2 Second group L2a Front group L2b Rear group SP Aperture G Glass plate FI Projected object d d-line g g-line S Sagittal image plane M Meridional image plane

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-67113 (JP, A) JP-A-61-231517 (JP, A) JP-A-7-77654 (JP, A) JP-A-6-76 11650 (JP, A) JP-A-1-185607 (JP, A) JP-A-5-19164 (JP, A) JP-A-5-45582 (JP, A) JP-A-5-27166 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 15/16

Claims (4)

(57) [Claims] 1. A zoom lens comprising, in order from a magnification side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, wherein the first lens unit is configured to perform zooming from a wide-angle end to a telephoto end. The second group is moved monotonously to the enlargement side by moving it with a convex locus on the reduction side,
The first group includes a negative first lens having both concave lens surfaces, a meniscus-shaped negative second lens having a convex surface facing the reduction side, and a positive third lens having a convex surface facing the enlargement side. Second
The group includes a diaphragm, a fourth lens having a positive convex surface on both lens surfaces, a fifth positive meniscus lens having a convex surface facing the magnification side, a sixth negative lens, and a positive meniscus lens having a convex surface facing the magnification side. The seventh lens, a meniscus-shaped negative eighth lens having a convex surface facing the magnification side, a positive ninth lens with both lens surfaces convex, and a negative tenth lens with both lens surfaces concave. The bonded first lens, the positive eleventh lens having both lens surfaces convex, the positive twelfth lens having a strong refractive power convex surface on the reduction side, and the positive second lens having a strong refractive power convex surface on the enlargement side A zoom lens comprising: a cemented second lens in which a thirteenth lens and a negative fourteenth lens whose both lens surfaces are concave are joined to each other; and a negative fifteenth lens having a concave surface having a strong refractive power directed to the enlargement side. . 2. Considering the stop as one surface, counting from the magnification side, the radius of curvature of the i-th lens surface is Ri, the i-th lens thickness or air gap is Di, and the material of the i-th lens is refracted. When the ratio and Abbe number are Ni and νi, the refractive power of the i-th lens is φi, and the focal length at the wide-angle end of the entire system is fw. The zoom lens according to claim 1, wherein the following condition is satisfied. 3. A zoom lens comprising, in order from the enlargement side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, wherein the first lens unit performs zooming from a wide-angle end to a telephoto end. The second group is moved monotonously to the enlargement side by moving it with a convex locus on the reduction side,
The first group includes a negative first lens having both concave lens surfaces, a meniscus-shaped negative second lens having a convex surface facing the reduction side, and a positive third lens having a convex surface facing the enlargement side. Second
The group includes a stop, a fourth lens having a positive convex surface on both lens surfaces, a fifth positive meniscus lens having a convex surface facing the magnification side, a sixth negative lens, and a positive meniscus lens having a convex surface facing the magnification side. The seventh lens, a meniscus negative eighth lens having a convex surface facing the enlargement side, a positive ninth lens with both lens surfaces convex, and a negative tenth lens with both lens surfaces concave. Bonded first lens, a positive eleventh lens having both lens surfaces convex, a bonded second lens obtained by bonding a negative twelfth lens and a positive thirteenth lens having both convex lens surfaces, and a convex surface on the magnification side Meniscus-shaped positive fourteenth lens with
A zoom lens comprising a negative fifteenth lens having a concave surface having a strong refractive power directed toward the enlargement side. 4. Considering the stop as one surface, counting from the magnification side, the radius of curvature of the i-th lens surface is Ri, the i-th lens thickness or air gap is Di, and the material of the i-th lens is refracted. When the ratio and the Abbe number are Ni and νi, the refractive power of the eleventh lens and the cemented second lens are φ11 and φA, respectively, and the focal length at the wide-angle end of the entire system is fw. The zoom lens according to claim 3, wherein the following condition is satisfied.