JPH0921953A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens provided with prescribed back focus and for projection of wide angle of view. SOLUTION: This lens is constituted in such a way that two lens groups of a first group L1 of negative refracting power and a second group L2 of positive refracting power are provided sequentially from a first conjugate point side with longer distance, and variable magnification from a wide angle terminal to a telescopic terminal is performed by moving both lens groups so as to simply reduce the interval of both lens groups, and the first lens group L1 consists of two lens groups of an 11th group L11 and a 12th group L12 setting the maximum lens interval as a boundary, and the second group L2 consists of two lens groups of a 21th group L21 and a 22th group L22 setting the longest interval as the boundary, and the 11th group L11 consists of four lenses of two negative lenses formed in meniscus shape making its projecting surface direct the first conjugate point side, a positive lens with refracting surface resistant for the first conjugate point side, and a negative lens whose both lens surfaces are formed in recessed shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, which is suitable as a projection lens for a liquid crystal projection television for projecting an image displayed on a liquid crystal display device or a color liquid crystal display device on a screen surface. Relates to a zoom lens composed of two lens groups.

[0002]

2. Description of the Related Art Conventionally, various liquid crystal projections have been proposed in which an image displayed on a liquid crystal display device or a plurality of color liquid crystals is optically superposed and projected on a screen surface by a projection lens.

As a projection lens generally used for liquid crystal projection, it is necessary to dispose various optical members such as a reflection mirror and a dichroic mirror between the final lens surface and the liquid crystal display element (between back focus), so that a long back focus is required. In addition, it is required to have high optical performance.

As a zoom lens for liquid crystal projection, for example, in Japanese Unexamined Patent Publication No. 5-27174, a positive first group that moves only from the enlargement side when focusing is performed, a negative second group for zooming, and an image associated with zooming. A finite-distance zoom lens composed of four lens units, a negative third lens unit for correcting surface fluctuations and a fixed positive fourth lens unit, has been proposed.

[0005]

Generally, in order to project a liquid crystal display device on a screen surface at various projection magnifications, it is necessary to configure the projection lens with a wide-angle zoom lens while reducing the size of the entire device and This is convenient because the projection magnification can be changed arbitrarily and quickly. However, it is very difficult to satisfactorily correct various aberrations and obtain high optical performance over the entire zoom range.

In the zoom lens proposed in the above-mentioned Japanese Patent Laid-Open No. 5-27174, the variation of distortion aberration is large from the wide-angle end to the intermediate zoom position. Therefore, for example, as shown in FIGS. 21A and 21B, two projection images SA and SB are displayed on the screen surface S by using two projectors A and B in order to improve the brightness of the projection image. If two images are to be observed in superimposition with each other, the two projected images SA and SB will be displaced around the screen and the image quality will be degraded.

The present invention is composed of two lens groups as a whole, and by appropriately setting the lens configuration of each lens group, the projection field angle is wide, and aberration fluctuations due to zooming are satisfactorily corrected. An object of the present invention is to provide a zoom lens that is suitable for, for example, a liquid crystal projector and that can easily obtain a long back focus while properly correcting distortion and maintaining good optical performance over the entire zoom range.

[0008]

A zoom lens according to a first aspect of the present invention comprises two lenses, a first group having a negative refracting power and a second group having a positive refracting power, in order from a first conjugate point side having a longer distance. Have a group,
Zooming from the wide-angle end to the telephoto end is performed by moving both lens groups so that the distance between the two lens groups decreases monotonically, and the first lens group is separated from the eleventh lens group by the largest lens distance. The second lens group is composed of two lens groups of 12 groups, the second group is composed of two lens groups of a 21st group and a 22nd group with the longest lens interval as a boundary, and the 11th group is from the first conjugate point side. Two negative meniscus lenses L111 and N112 having a convex surface facing the first conjugate point side, a negative lens L112, a positive lens L113 having a strong refractive surface on the first conjugate point side, and a negative lens having both concave lens surfaces. It is characterized by being composed of four L114 lenses.

The zoom lens according to the second aspect of the invention has two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, in order from the first conjugate point side having the longer distance, and has a wide angle of view. The zooming from the end to the telephoto end is performed by moving both lens groups so that the distance between both lens groups monotonously decreases. The second lens unit is composed of two lens units of a 21st lens unit and a 22nd lens unit at the longest lens interval, and the 11th lens unit is arranged in order from the first conjugate point side. A meniscus negative lens L111 having a convex surface directed toward the first conjugate point side, and a meniscus positive lens L11 having a convex surface directed toward the first conjugate point side
2, a meniscus negative lens L113 having a convex surface facing the first conjugate point side, a positive lens L114 having a strong refracting surface on the first conjugate point side, and a negative lens L1 having both concave lens surfaces.
It is characterized by being made up of 5 lenses of 15.

A zoom lens according to a third aspect of the invention has two lens groups, a first group having a negative refracting power and a second group having a positive refracting power, in order from the first conjugate point side having a longer distance, and has a wide angle. The zooming from the end to the telephoto end is performed by moving both lens groups so that the distance between both lens groups monotonously decreases. The second lens unit is composed of two lens units of a 21st lens unit and a 22nd lens unit at the longest lens interval, and the 11th lens unit is arranged in order from the first conjugate point side. It is composed of three lenses: a positive lens L111 having both convex lens surfaces, a meniscus negative lens L112 having a convex surface facing the first conjugate point side, and a positive lens L113 having a strong refractive surface on the first conjugate point side. It is characterized by

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are lens sectional views at the wide-angle end of Numerical Embodiments 1 and 2 as the first invention, and FIG. 3 is a lens sectional view at the wide-angle end of Numerical Embodiment 3 as the second invention. 4 and 5 are lens cross-sectional views at the wide-angle end of Numerical Embodiments 4 and 5 as the third invention.

FIGS. 6, 7, and 8 are aberration diagrams of the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 1, and FIGS. 9, 10 and 11 show the wide-angle end, the middle, and the telephoto end of Numerical Embodiment 2. Aberration diagram, FIG.
FIGS. 13 and 14 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Example 3, and FIGS. 15, 16 and 17 are aberration diagrams at the wide-angle end, the middle, and the telephoto end of Numerical Example 4, and FIG. 19 and 20
[Fig. 4] is an aberration diagram at a wide-angle end, a middle end, and a telephoto end of Numerical Example 5.

In the lens sectional views of FIGS. 1 to 5, L1 is a first lens unit having a negative refractive power, and L2 is a second lens unit having a positive refractive power. The first lens unit L1 is composed of two lens units, that is, an eleventh lens unit L11 and a twelfth lens unit L12 with a widest air space (lens unit space) as a boundary. Similarly, the second group L2 is divided into the second group L21 and the second group L22 by the widest air gap.
It consists of two lens groups. S is a screen surface (projection surface), and P is an original image (projection surface) of a liquid crystal display element, a color liquid crystal or the like. SP is a diaphragm and LP is a fixed diaphragm.

The screen surface S and the original image P have a conjugate relationship. Generally, the screen surface S is at a conjugate point with a longer distance (first conjugate point), and the original image P is at a conjugate point with a shorter distance ( This corresponds to the second conjugate point). For zooming from the wide-angle end to the telephoto end, as shown by the arrow, the first lens unit L1 is moved non-linearly in the direction of the screen surface S, and the second lens unit L2 is moved in the direction of the screen surface S so that the distance between both lens groups is monotonous. We are moving to decrease.

In the first invention of FIGS. 1 and 2, the eleventh group L11
Are two meniscus-shaped negative lenses L111 and L having convex surfaces facing the first conjugate point side in order from the first conjugate point side.
112, a positive lens L having a strong refractive surface on the side of the first conjugate point
113 and four negative lenses L114 each having a concave lens surface.

In the second aspect of the invention shown in FIG. 3, the meniscus negative lens L111 having a convex surface facing the first conjugate point side of the eleventh group L11 is arranged in this order from the first conjugate point side to the first conjugate point side. A positive meniscus lens L112 having a convex surface, and a negative meniscus lens L11 having a convex surface on the side of the first conjugate point.
3, a positive lens L11 having a strong refractive surface on the side of the first conjugate point
4 and five negative lenses L115 each having a concave lens surface.

In the third invention of FIGS. 4 and 5, the eleventh lens unit L
11 is a positive lens L111 whose lens surfaces are convex in order from the first conjugate point side, a meniscus negative lens L112 having a convex surface facing the first conjugate point side, and a strong refracting surface on the first conjugate point side. The positive lens L113 has three lenses.

As a result, the pin-cushion distortion aberration and other various aberrations generated by the negative lens group are satisfactorily corrected over the entire zoom range while ensuring a predetermined back focus.

The first invention of FIGS. 1 and 2, and FIG.
In the second invention, the twelfth lens group is composed of two lenses, in order from the first conjugate point side, a negative lens L121 having both concave lens surfaces and a positive lens L122 having both convex lens surfaces.

In particular, the negative lens L121 and the positive lens L122
Are made of materials with different Abbe numbers. In the third invention of FIGS. 4 and 5, the twelfth lens unit has a negative lens L12 having a strong refracting surface on the second conjugate point side, which is the shorter distance from the first conjugate point side.
1, a negative lens L12 having a strong refractive surface on the first conjugate point side
2, and a positive lens L having a strong refracting surface on the first conjugate point side
It is composed of three lenses 123. In particular, a material having an Abbe number larger than that of the material of the positive lens is used for the negative lens. This satisfactorily corrects variations in various aberrations such as lateral chromatic aberration and longitudinal chromatic aberration that accompany zooming, and ensures high optical performance over the entire zoom range.

In the first, second and third inventions, when the negative lens surface in the eleventh group has an aspherical surface, an aspherical surface having a shape in which the negative refractive power becomes weaker from the lens center to the lens periphery is used. In the case where the positive lens surface of the 11th group has an aspherical surface, distortion is satisfactorily corrected by using an aspherical surface in which the positive refractive power increases from the lens center to the lens periphery. Further, when the positive lens in the second group has an aspherical surface, the negative lens in the second group has an aspherical surface using an aspherical surface whose positive refractive power becomes weaker from the lens center to the lens periphery. In this case, the spherical aberration is satisfactorily corrected by using an aspherical surface having a shape in which the negative refracting power becomes stronger from the lens center toward the periphery.

The zoom lens aimed at by the present invention can be achieved by satisfying the above-mentioned various conditions, but in order to keep the optical performance of the entire screen good, at least one of the following conditions is satisfied. It is good to let

(B) The eleventh lens group and the second lens group each have at least one aspherical surface. In particular, by providing an aspherical surface on the lens surface where the incident height of the off-axis chief ray is high in this way, distortion is effectively corrected over the entire zoom range.

(B) When the lens surface having positive refracting power has an aspherical surface, the 22nd group has an aspherical surface having a shape in which the positive refracting power becomes weaker from the lens center to the lens periphery, and has a negative refracting power. If the lens surface has an aspherical surface, it means that the lens surface has an aspherical surface in which the negative refracting power becomes stronger from the lens center to the lens periphery. As a result, distortion and various other aberrations are well corrected over the entire zoom range.

(C) The twenty-first lens unit includes three lenses, in order from the first conjugate point side, a positive lens L211, a meniscus negative lens L212 having a convex surface facing the second conjugate point side having a shorter distance, and a positive lens L213. It consists of a lens.
As a result, spherical aberration and coma are mainly corrected in good balance.

(D) The first invention of FIGS. 1 and 2 and the second invention of FIG.
In the invention, in the 22nd group, in order from the first conjugate point side, the negative lens L221 having both concave lens surfaces, the positive lens L222 having both convex lens surfaces, and the negative lens L223 having a strong refractive surface on the first conjugate point side Is a positive lens L224 having a strong refracting surface on the side of the second conjugate point which is shorter, and a positive lens L225 having both convex lens surfaces.
Thereby, the spherical aberration and the coma aberration are mainly corrected well.

(E) In the third invention of FIGS. 4 and 5, the 22nd invention
The group includes, in order from the first conjugate point side, a negative lens L221 having both concave lens surfaces, a positive lens L222 having both convex lens surfaces, and a first lens element L222.
A meniscus negative lens L22 having a convex surface on the conjugate point side
3, with a strong refracting surface on the second conjugate point side of the shorter distance 2
It is configured by five positive lenses L224 and L225. Thereby, the spherical aberration and the coma aberration are mainly corrected well.

(F) The distance from the final lens surface of the second lens unit at the wide-angle end to the second conjugate point having the shorter distance at the wide-angle end when the first conjugate point is infinity is bfw, and the focal point of the entire system at the wide-angle end. The distance is fw, and the focal lengths of the first and second groups are f and f, respectively.
1, f2, where ew is the principal point distance between the first and second groups at the wide-angle end 1.2 <bfw / fw (1) 0.3 <-f1 / f2 <1.5 (2) 0.3 <-f1 / fw <2 (3) 0.5 <f2 / fw <1.8 (4) 0.3 <ew / fw <2 (5) To satisfy the following condition.

Conditional expression (1) limits the ratio between the back focus at the wide-angle end (short focal end) and the focal length of the entire system at the wide-angle end. In a region where the lower limit of conditional expression (1) is exceeded, the back force becomes too short, and there is no space for a dichroic mirror or the like for synthesizing original images composed of three-color liquid crystal display elements, which is not preferable.

Conditional expression (2) limits the ratio of the focal lengths of the first lens unit and the second lens unit. In a region where the lower limit of conditional expression (2) is exceeded, the refracting power (power) of the first group becomes too strong, so that the curvature of field becomes excessive and the distortion becomes under. Further, in the area exceeding the upper limit of the conditional expression (2), the focal length of the first lens unit becomes too long, and the focal length of the entire system also becomes long, so that the projection distance for obtaining a large projected image becomes long. Not good.

Conditional expression (3) limits the ratio of the focal length of the first lens unit to the focal length of the entire system at the wide-angle end. The field curvature becomes excessive in a region exceeding the lower limit of the conditional expression (3), and the field curvature becomes under in a region exceeding the upper limit of the conditional expression (3), which is not good.

Conditional expression (4) limits the ratio of the focal length of the second lens group to the focal length of the entire system at the wide-angle end. In the region where the lower limit of conditional expression (4) is exceeded, the focal length of the second lens group is reduced. Is too short, the back focus becomes short, and in the region exceeding the upper limit of conditional expression (4), the focal length of the second lens unit becomes too long, which is not preferable because the total lens length becomes large.

Conditional expression (5) limits the ratio of the principal point distance between the first and second lens units at the wide-angle end and the focal length of the entire system at the wide-angle end. In the region where the lower limit of conditional expression (5) is exceeded, the zoom ratio cannot be large, and in the region where the upper limit of conditional expression (5) is exceeded, the total lens length becomes large, which is not good.

In the present invention, in terms of aberration correction, it is more preferable to set the numerical limits of conditional expressions (1) to (5) as follows.

1.6 <bfw / fw (1a) 0.45 <-f1 / f2 <1.2 (2a) 0.5 <-f1 / fw <1.5 ((a)) 3a) 0.7 <f2 / fw <1.5 (4a) 0.7 <ew / fw <1.6 (5a) (g) Negative lens and positive lens in the 11th group The average values of the Abbe numbers of the materials are ν11N, ν11P,
When the average values of the Abbe numbers of the materials of the negative lens and the positive lens in the group are ν12N and ν12P, respectively, -15 <ν11N-ν11P <15 (6) 15 <ν12N-ν12P <40 (7) ) To satisfy the following condition.

The conditional expressions (6) and (7) are mainly for favorably correcting lateral chromatic aberration. In the area exceeding the lower limit of conditional expression (6), lateral chromatic aberration becomes under, and in the area exceeding the upper limit of conditional expression (6), achromatism is performed at a high incident height of the off-axis chief ray. However, this is not good because a lot of high-order chromatic aberration of magnification occurs.

It is not preferable because the chromatic aberration of magnification becomes under in the range exceeding the lower limit value of the conditional expression (7), and the chromatic aberration of magnification becomes excessive in the range exceeding the upper limit value of the conditional expression (7).

In the present invention, it is more preferable to set the numerical limits of conditional expressions (6) and (7) as follows.

-12 <ν11N-ν11P <10 (6a) 18 <ν12N-ν12P <32 (7a) Next, numerical examples of the present invention will be described. R in numerical examples
i is the radius of curvature of the i-th lens surface in order from the screen side, Di is the i-th lens thickness and air gap from the screen side, and Ni and νi are the refractive indices of the glass of the i-th lens in order from the screen side, respectively. And Abbe number. Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. The aspherical shape has an X axis in the optical axis direction, an H axis in the direction perpendicular to the optical axis, and a light traveling direction is positive, and R is a paraxial radius of curvature, K, A ₂ , A ₃ , A ₄ , A ₅ , A. _{When 6} is the aspherical coefficient,

[0040]

[Equation 1] It is represented by the following equation. Also, "D-0X" is "10 ^-X "
Means

Numerical Example 1 f = 108.80 fno = 1: 3.6 to 4.5 2ω = 45 ° to 30.8 ° R 1 = 71.79 D 1 = 5.00 N 1 = 1.51633 ν 1 = 64.2 R 2 = 49.50 D 2 = 20.57 R 3 = 94.29 D 3 = 3.70 N 2 = 1.51633 ν 2 = 64.2 R 4 = 53.24 D 4 = 5.20 R 5 = 51.82 D 5 = 8.10 N 3 = 1.51633 ν 3 = 64.2 R 6 = 156.15 D 6 = 3.15 R 7 = -566.78 D 7 = 2.35 N 4 = 1.51633 ν 4 = 64.2 R 8 = 114.71 D 8 = 28.86 R 9 = -44.22 D 9 = 2.30 N 5 = 1.60311 ν 5 = 60.7 R10 = 130.11 D10 = 0.27 R11 = 147.84 D11 = 6.70 N 6 = 1.83400 ν 6 = 37.2 R12 = -129.68 D12 = Variable R13 = 2232.65 D13 = 5.25 N 7 = 1.51633 ν 7 = 64.2 R14 = -156.23 D14 = 4.53 R15 = -54.55 D15 = 2.70 N 8 = 1.62299 ν 8 = 58.2 R16 = -74.79 D16 = 0.20 R17 = 74.79 D17 = 12.40 N 9 = 1.48749 ν 9 = 70.2 R18 = -118.72 D18 = 18.44 R19 = -104.94 D19 = 2.30 N10 = 1.78590 ν10 = 44.2 R20 = 142.25 D20 = 1.21 R21 = 253.00 D21 = 9.50 N11 = 1.48749 ν11 = 70.2 R22 = -66.51 D22 = 3.39 R23 = -58.58 D23 = 2.90 N12 = 1.78590 ν12 = 44.2 R24 = -158.79 D24 = 0.20 R25 = 774.64 D25 = 8.70 N13 = 1.49700 ν13 = 81.6 R26 = -81.74 D26 = 0.20 R27 = 800.46 D27 = 7.05 N14 = 1.48749 ν14 = 70.2 R28 = -110.00 D28 = Variable R29 = Fixed Aperture \ Focal length 108.80 136.10 163.40 Variable spacing \ D12 27.91 13.18 3.37 D28 0.00 34.39 68.79 Aspheric R1 surface R = 7.179 D + 01 K = 8.253 D-01 A ₂ = 2.505 D-07 A ₃ = 4.381 D-12 A ₄ = 8.135 D-14 A ₅ = -4.999 D-17 A ₆ = 1.856 D-20 Aspherical R28 surface R = -1.100 D + 02 K = -6.804 D- 01 A ₂ = 5.320 D-07 A ₃ = 2.211 D-10 A ₄ = -2.379 D-13 A ₅ = 1.987 D-16 A ₆ = -5.833 D-20 <Numerical Example 2> f = 108.61 fno = 1 : 3.6 to 4.5 2 ω = 45 ° to 30.8 ° R 1 = 67.00 D 1 = 5.00 N 1 = 1.51633 ν 1 = 64.2 R 2 = 47.64 D 2 = 12.65 R 3 = 91.73 D 3 = 3.70 N 2 = 1.51633 ν 2 = 64.2 R 4 = 68.01 D 4 = 8.77 R 5 = 55.84 D 5 = 7.68 N 3 = 1.51633 ν 3 = 64.2 R 6 = 128.14 D 6 = 4.24 R 7 = -537.03 D 7 = 2.00 N 4 = 1.51633 ν 4 = 64.2 R 8 = 91.96 D 8 = 34.82 R 9 = -42.11 D 9 = 2.30 N 5 = 1.60311 ν 5 = 60.7 R10 = 142.93 D10 = 0.28 R11 = 162.10 D11 = 6.69 N 6 = 1.83400 ν 6 = 37.2 R12 = -119.41 D12 = Variable R13 = (Aperture) D13 = 0.00 R14 = 1113.64 D14 = 6.36 N 7 = 1.51633 ν 7 = 64.2 R15 = -127.45 D15 = 3.86 R16 = -56.05 D16 = 2.7 0 N 8 = 1.72000 ν 8 = 50.3 R17 = -81.29 D17 = 0.19 R18 = 75.45 D18 = 12.47 N 9 = 1.51633 ν 9 = 64.2 R19 = -121.02 D19 = 15.51 R20 = -143.50 D20 = 2.69 N10 = 1.78590 ν10 = 44.2 R21 = 124.51 D21 = 1.73 R22 = 283.43 D22 = 9.09 N11 = 1.48749 ν11 = 70.2 R23 = -68.97 D23 = 4.03 R24 = -55.56 D24 = 2.90 N12 = 1.80610 ν12 = 41.0 R25 = -173.15 D25 = 0.20 R26 = 1334.20 D26 = 9.03 N13 = 1.48749 ν13 = 70.2 R27 = -75.61 D27 = 0.20 R28 = 837.60 D28 = 7.38 N14 = 1.48749 ν14 = 70.2 R29 = -104.92 D29 = Variable R30 = Fixed Aperture \ Focal Length 108.61 135.76 162.92 Variable Distance \ D12 27.16 13.01 3.57 D29 0.00 34.45 68.90 Aspheric surface R1 surface R = 6.700 D + 01 K = 8.503 D-01 A ₂ = 1.912 D-07 A ₃ = -3.255 D-14 A ₄ = 6.410 D-14 A ₅ = -4.410 D-17 A ₆ = 1.665 D-20 Aspheric surface R 29 surface R = -1.049 D + 02 K = -2.264 D-01 A ₂ = 5.806 D-07 A ₃ = 2.177 D-10 A ₄ = -1.886 D-13 A ₅ = 1.482 D-16 A ₆ = -3.475 D-20 <Numerical Example 3> f = 107.98 fno = 1: 3.6 to 4.5 2ω = 45.2 ° to 31 ° R 1 = 64.45 D 1 = 5.00 N 1 = 1.60311 ν 1 = 60.7 R 2 = 45.98 D 2 = 5.56 R 3 = 52.55 D 3 = 5.84 N 2 = 1.51633 ν 2 = 64.2 R 4 = 68.69 D 4 = 2.99 R 5 = 96.15 D 5 = 3.50 N 3 = 1.60311 ν 3 = 60.7 R 6 = 47.69 D 6 = 11.78 R 7 = 50.20 D 7 = 8.00 N 4 = 1.51633 ν 4 = 64.2 R 8 = 169.18 D 8 = 4.28 R 9 = -335.38 D 9 = 2.00 N 5 = 1.60311 ν 5 = 60.7 R10 = 134.11 D10 = 26.27 R11 = -43.63 D11 = 2.00 N 6 = 1.60311 ν 6 = 60.7 R12 = 145.86 D12 = 1.94 R13 = 200.15 D13 = 6.68 N 7 = 1.83400 ν 7 = 37.2 R14 = -118.67 D14 = Variable R15 = (Aperture) D15 = 0.54 R16 = 342.95 D16 = 4.70 N 8 = 1.51633 ν 8 = 64.2 R17 =- 166.09 D17 = 5.76 R18 = -58.80 D18 = 2.50 N 9 = 1.77250 ν 9 = 49.6 R19 = -82.90 D19 = 0.12 R20 = 77.27 D20 = 10.76 N10 = 1.51633 ν10 = 64.2 R21 = -117.30 D21 = 17.65 R22 = -119.91 D22 = 2.33 N11 = 1.78590 ν11 = 44.2 R23 = 135.29 D23 = 3.13 R24 = 306.18 D24 = 7.63 N12 = 1.48749 ν12 = 70.2 R25 = -76.20 D25 = 3.46 R26 = -59.14 D26 = 2.80 N13 = 1.80610 ν13 = 41.0 R27 = -211.59 D27 = 0.20 R28 = 2391.07 D28 = 7.89 N14 = 1.48749 ν14 = 70.2 R29 = -69.64 D29 = 0.20 R30 = 342.89 D30 = 6.50 N15 = 1.48749 ν15 = 70.2 R31 = -110.00 D31 = Variable R32 = Fixed Aperture \ Focal Length 107.98 134.98 161.97 Yes Interval \ D14 27.57 12.72 2.83 D31 0.00 32.94 65.88 aspherical surface R1 R = 6.445 D + 01 K = 7.311 D-01 A 2 = 1.539 D-07 A 3 = 3.127 D-11 A 4 = 2.531 D14 A 5 = -2.369 D-17 A ₆ = 1.169 D-20 Aspherical R31 surface R = -1.100 D + 02 K = -5.454 D-01 A ₂ = 6.294 D-07 A ₃ = 1.650 D-10 A ₄ = -1.052 D -13 A ₅ = 8.892 D-17 A ₆ = -2.415 D-20 <Numerical Example 4> f = 109.15 fno = 1: 3.6 to 4.5 2 ω = 44.8 ° to 30.8 ° R 1 = 536.79 D 1 = 5.12 N 1 = 1.51633 ν 1 = 64.2 R 2 = -1536.51 D 2 = 0.20 R 3 = 117.25 D 3 = 4.50 N 2 = 1.60311 ν 2 = 60.7 R 4 = 61.61 D 4 = 5.95 R 5 = 90.81 D 5 = 13.18 N 3 = 1.51633 ν 3 = 64.2 R 6 = -427.89 D 6 = 16.68 R 7 = 207.06 D 7 = 3.00 N 4 = 1.60311 ν 4 = 60.7 R 8 = 36.39 D 8 = 13.51 R 9 = -59.95 D 9 = 2.80 N 5 = 1.60311 ν 5 = 60.7 R10 = 320.32 D10 = 0.20 R11 = 83.62 D11 = 4.96 N 6 = 1.83400 ν 6 = 37.2 R12 = 2522.71 D12 = Variable R13 = (Aperture) D13 = 4.30 R14 = 273.13 D14 = 5.46 N 7 = 1.69680 ν 7 = 55.5 R15 = -202.55 D15 = 3.87 R16 = -59.08 D16 = 3.00 N 8 = 1.78590 ν 8 = 44.2 R17 = -75.05 D17 = 0.52 R18 = 114.91 D18 = 5.53 N 9 = 1.51823 ν 9 = 59. 0 R19 = -436.85 D19 = 15.77 R20 = -161.36 D20 = 2.97 N10 = 1.80610 ν10 = 41.0 R21 = 109.11 D21 = 2.02 R22 = 106.68 D22 = 8.62 N11 = 1.49700 ν11 = 81.6 R23 = -133.59 D23 = 0.20 R24 = 287.05 D24 = 2.97 N12 = 1.83400 ν12 = 37.2 R25 = 128.21 D25 = 3.40 R26 = -3067.63 D26 = 5.65 N13 = 1.51633 ν13 = 64.2 R27 = -93.98 D27 = 0.13 R28 = -845.75 D28 = 5.64 N14 = 1.51633 ν14 = 64.2 R29 =- 102.21 D29 = Variable R30 = Fixed Aperture \ focal length 109.16 136.45 163.74 Variable spacing \ D12 43.99 15.58 26.95 D29 0.00 57.59 28.79 Aspherical R5 surface R = 9.081 D + 01 K = -9.936 D-02 A ₂ = 8.342 D-09 A ₃ = -1.715 D-11 A ₄ = -1.296 D-15 A ₅ = -3.102 D-19 Aspheric surface R18 surface R = 1.149 D + 02 K = -2.984 D + 00 A ₂ = 8.658 D-08 A ₃ = 1.153 D-11 A ₄ = 4.377 D-15 A ₅ = -3.353 D-18 <Numerical Example 5> f = 108.72 fno = 1: 3.6 to 4.5 2 ω = 45 ° to 30.8 ° R 1 = 310.26 D 1 = 6.23 N 1 = 1.51633 ν 1 = 64.2 R 2 = -5026.20 D 2 = 0.20 R 3 = 104.05 D 3 = 4.50 N 2 = 1.60311 ν 2 = 60.7 R 4 = 54.60 D 4 = 9.02 R 5 = 107.96 D 5 = 10.58 N 3 = 1.51633 ν 3 = 64.2 R 6 = -477.51 D 6 = 18.50 R 7 = 193.30 D 7 = 3.00 N 4 = 1.60311 ν 4 = 60.7 R 8 = 38.86 D 8 = 11.63 R 9 = -61.77 D 9 = 2.80 N 5 = 1.60311 ν 5 = 60.7 R10 = 223.90 D10 = 0.20 R11 = 82.79 D11 = 5.11 N 6 = 1.83400 ν 6 = 37.2 R12 = -3717.41 D12 = Variable R13 = (Aperture) D13 = 4.11 R14 = 284.69 D14 = 5.74 N 7 = 1.69680 ν 7 = 55.5 R15 = -165.89 D15 = 3.47 R16 = -59.23 D16 = 3.00 N 8 = 1.78590 ν 8 = 44.2 R17 = -80.13 D17 = 0.52 R18 = 117.58 D18 = 5.56 N 9 = 1.51823 ν 9 = 59.0 R19 = -445.97 D19 = 16.97 R20 = -161.61 D20 = 2.97 N10 = 1.80610 ν10 = 41.0 R21 = 104.10 D21 = 2.12 R22 = 107.88 D22 = 7.81 N11 = 1.49700 ν11 = 81.6 R23 = -140.97 D23 = 0.20 R24 = 276.79 D24 = 2.97 N12 = 1.83400 ν12 = 37.2 R25 = 131.43 D25 = 2.66 R26 = 1419.51 D26 = 5.87 N13 = 1.51633 ν13 = 64.2 R27 = -97.28 D27 = 0.16 R28 = -1325.52 D28 = 5.80 N14 = 1.51633 ν14 = 64.2 R29 = -104.08 D29 = variable R30 = fixed aperture \ focal length 108.73 135.91 163.09 variable spacing \ D12 42.38 25.53 14.30 D29 0.00 28.95 57.91

[0042]

[Table 1]

[0043]

As described above, according to the present invention, as a whole, it is composed of two lens groups, and by appropriately setting the lens configuration of each lens group, the projection angle of view is wide and the aberration associated with zooming is large. Achieves a zoom lens suitable for liquid crystal projectors, for example, by correcting fluctuations satisfactorily, especially by correcting distortion aberrations, and easily maintaining a long back focus while maintaining good optical performance over the entire zoom range. can do.

[Brief description of 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 lens cross-sectional view at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 3 is a lens cross-sectional view at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 4 is a lens cross-sectional view at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 5 is a lens cross-sectional view at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 6 is an aberration diagram at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 7 is an intermediate aberration diagram of Numerical Example 1 of the present invention.

FIG. 8 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 9 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 10 is an intermediate aberration diagram of Numerical example 2 of the present invention.

FIG. 11 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 12 is an aberration diagram at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 13 is an intermediate aberration diagram of Numerical Example 3 of the present invention.

FIG. 14 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

FIG. 15 is an aberration diagram at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 16 is an intermediate aberration diagram of Numerical example 4 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end according to Numerical Example 4 of the present invention.

FIG. 18 is an aberration diagram at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 19 is an intermediate aberration diagram of Numerical Example 5 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end according to Numerical Example 5 of the present invention.

FIG. 21 is an explanatory diagram of deviation of a projected image when the projection lens has distortion.

[Explanation of symbols]

 L1 1st group L2 2nd group L21 21st group L22 22nd group S screen P original image S sagittal image surface M meridional image surface d d line FF line C C line C sine condition

Claims (13)

[Claims] 1. A first lens unit having a negative refractive power and a second lens unit having a positive refractive power are arranged in this order from the first conjugate point side having a longer distance, and a lens unit from a wide-angle end to a telephoto end is provided. The zooming is performed by moving both lens groups so that the distance between the two lens groups monotonously decreases, and the first lens group has two lens groups, the 11th lens group and the 12th lens group, with the largest lens distance as a boundary. The second group is composed of two lens groups, a 21st group and a 22nd group, with the longest lens interval as a boundary, and the 11th group is arranged in order from the first conjugate point side to the first conjugate point side. It is composed of two meniscus negative lenses L111 having convex surfaces facing to each other, a negative lens L112, a positive lens L113 having a strong refracting surface on the side of the first conjugate point, and a negative lens L114 having both concave lens surfaces. A zoom lens that is characterized by 2. The optical system has two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the first conjugate point side having a longer distance, and are arranged from a wide-angle end to a telephoto end. The zooming is performed by moving both lens groups so that the distance between the two lens groups monotonously decreases, and the first lens group has two lens groups, the 11th lens group and the 12th lens group, with the largest lens distance as a boundary. The second group is composed of two lens groups, a 21st group and a 22nd group, with the longest lens interval as a boundary, and the 11th group is arranged in order from the first conjugate point side to the first conjugate point side. A negative meniscus lens L111 having a convex surface facing the first conjugate point, a positive meniscus lens L112 having a convex surface facing the first conjugate point side, a negative meniscus lens L113 having a convex surface facing the first conjugate point side, A positive lens L114 having a strong refracting surface on the one conjugate point side, and a negative lens having concave surfaces on both lens surfaces. A zoom lens characterized by being made up of five lenses, L115. 3. A first lens unit having a negative refractive power and a second lens unit having a positive refractive power are arranged in this order from the first conjugate point side having a longer distance, and the two lens units are provided from a wide-angle end to a telephoto end. The zooming is performed by moving both lens groups so that the distance between the two lens groups monotonously decreases, and the first lens group has two lens groups, the 11th lens group and the 12th lens group, with the largest lens distance as a boundary. The second group is composed of two lens groups of a 21st group and a 22nd group with a longest lens interval as a boundary, and the 11th group has a convex surface on both lens surfaces in order from the first conjugate point side. Positive lens L111, the first
A meniscus negative lens L11 having a convex surface facing the conjugate point
2, and a zoom lens comprising three lenses of a positive lens L113 having a strong refracting surface on the side of the first conjugate point. 4. The twelfth lens unit comprises, in order from the first conjugate point side, two lenses, a negative lens L121 having both concave lens surfaces and a positive lens L122 having both convex lens surfaces. Item 1 or 2 zoom lens. 5. The negative lens L121 having a strong refractive surface on the side of the second conjugate point, which is the shorter distance from the first conjugate point side, and the negative lens having a strong refractive surface on the side of the first conjugate point, in the twelfth group. L
4. The zoom lens according to claim 3, wherein the zoom lens comprises three lenses 122, and a positive lens L123 having a strong refractive surface on the first conjugate point side. 6. The zoom lens according to claim 1, wherein each of the 11th group and the 2nd group has at least one aspherical surface. 7. The eleventh group has an aspherical surface whose negative refracting power becomes weaker from the lens center to the lens periphery when the lens surface having a negative refracting power has an aspherical surface. 7. The zoom lens according to claim 6, wherein when the lens has an aspherical surface, the aspherical surface has a positive refractive power that increases from the lens center to the lens periphery. 8. If the lens surface having a positive refracting power has an aspherical surface, the 22nd group has an aspherical surface having a shape in which the positive refracting power becomes weaker from the center of the lens to the periphery of the lens. 8. The zoom lens according to claim 6, wherein the lens surface has an aspherical surface in which the negative refracting power becomes stronger from the lens center to the lens periphery. 9. The twenty-first lens group includes three lenses, a positive lens L211, a meniscus negative lens L212 having a convex surface directed toward the second conjugate point side having a shorter distance, and a positive lens L213 in order from the first conjugate point side. 9. The zoom lens according to claim 1, wherein the zoom lens comprises a lens. 10. The negative lens L221 having concave surfaces on both lens surfaces in order from the first conjugate point side, the positive lens L222 having convex surfaces on both lens surfaces, and the negative lens having a strong refractive surface on the first conjugate point side. 4. A lens L223, a positive lens L224 having a strong refracting surface on the side of the second conjugate point having a shorter distance, and a positive lens L225 having a convex surface on both lens surfaces, which are five lenses. , 4, 6, 7, 8 or 9
Zoom lens. 11. The meniscus-shaped lens element having a negative lens L221 having concave surfaces on both sides, a positive lens L222 having convex surfaces on both lens surfaces, and a convex surface facing the first conjugate point, in the order from the first conjugate point side. Negative lens L223, two positive lenses L224, L having a strong refracting surface on the side of the second conjugate point having a shorter distance.
The zoom lens according to claim 3, 5, 6, 7, 8 or 9, wherein the zoom lens comprises five lenses of 225. 12. A second lens having a shorter distance from the final lens surface of the second lens unit at the wide-angle end when the first conjugate point is at infinity.
The distance to the conjugate point is bfw, the focal length of the entire system at the wide-angle end is fw, and the focal lengths of the first group and the second group are f1,
f2, the distance between the principal points of the first group and the second group at the wide-angle end is e
When w is set, 1.2 <bfw / fw 0.3 <-f1 / f2 <1.5 0.3 <-f1 / fw <2 0.5 <f2 / fw <1.8 0.3 <ew / 12. The condition of fw <2 is satisfied, which is characterized in that
The zoom lens according to any one of 1. 13. The average values of the Abbe numbers of the materials of the negative lens and the positive lens in the 11th group are v11N and v11P, respectively.
When the average values of the Abbe numbers of the materials of the negative lens and the positive lens in the twelfth group are ν12N and ν12P, respectively, the condition of -15 <ν11N-ν11P <15 15 <ν12N-ν12P <40 is satisfied. Claims 1 to 12
The zoom lens according to any one of 1.