JPH11202199A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which projects an image of a small-sized and high-pixel-density display element and has astigmatism corrected excellently. SOLUTION: The zoom lens consists of a 1st negative group Gr1, a 2nd positive group Gr2, and a 3rd positive group Gr3 in order from the projection side and when the power is varied, the 1st group Gr1 and 2nd group Gr2 move along the optical axis Ax. The 3rd group Gr3 is equipped with a 1st negative meniscus lens M1 which is concave to the enlargement side and a 2nd meniscus lens M2 which consists of a cemented lens of a biconvex and biconcave lens from the enlargement side and is convex totally to the enlargement side and the radii r12 and r13 of curvature of the 1st meniscus lens M1 are properly set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, for example, a zoom lens suitable as a projection optical system for a projection apparatus (such as a liquid crystal projector for projecting an image of a display element such as a liquid crystal panel on a screen). It is about a lens.

[0002]

2. Description of the Related Art In recent years, high image quality of liquid crystal projectors (V
With the shift from GA to S-VGA and further to XGA), liquid crystal panels have been reduced in size and pixels. And miniaturization
In order to project an image of a display element with an increased number of pixels, a high-performance projection optical system having a higher resolution than before has been required.

[0003]

However, the configuration of the conventional projection optical system cannot sufficiently satisfy the required optical performance. For example, JP-A-64-467
The zoom lens proposed in Japanese Patent Publication No. 17 has no problem when the image circle is small as in a video camera, but it is difficult to suppress astigmatism when the image circle is large as in a liquid crystal projector. Point difference becomes a problem. If the number of constituent lenses is increased or the lens diameter is increased to suppress astigmatism, the entire optical system naturally becomes larger, and as a result,
It is difficult to reduce the size of the projector itself, and the cost is inevitable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in order to project an image of a display element having a reduced size and a higher number of pixels, and to correct astigmatism satisfactorily. It is intended to provide a lens.

[0005]

In order to achieve the above object, a zoom lens according to the present invention comprises, in order from the magnification side, a first unit having a negative power, a second unit having a positive power,
A third lens unit having a positive power, wherein the first lens unit and the second lens unit each move in the optical axis direction at the time of zooming, wherein the third lens unit is, in order from the magnification side, A first meniscus lens having a concave surface facing the enlargement side and having a negative power, and a cemented lens composed of a biconvex lens and a biconcave lens, and having a positive or negative power having a convex surface facing the enlargement side in total. The second meniscus lens, and the third group further includes at least one negative lens and at least one positive lens on a reduction side of the second meniscus lens, and the first meniscus lens Satisfies the following conditional expression. | (R _M1F + r _M1R ) / (r _M1F −r _M1R ) |> 3, where r _{M1F is the} radius of curvature of the enlarged side surface of the first meniscus lens, and r _M1R is the radius of curvature of the reduced side surface of the first meniscus lens. .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a zoom lens embodying the present invention will be described with reference to the drawings. The embodiment described below is a zoom lens suitable as a projection optical system for a projection device (for example, a liquid crystal projector), but can also be suitably used as an imaging optical system for an imaging device (for example, a video camera). Needless to say,

FIG. 1 is a lens configuration diagram showing the present embodiment, and shows the lens arrangement at the telephoto end [L]. An arrow mj (j = 1, 2, 3) in the lens configuration diagram indicates a j-th group (Grj) in zooming from the telephoto end (long focal length end) [L] to the wide-angle end (short focal length end) [S]. ) Are schematically shown. Also, in the lens configuration diagram, the surface with ri (i = 1, 2, 3, ...) is the i-th surface counted from the enlargement side (that is, the projection side), and each surface with di The shaft upper surface interval between groups is a variable interval that changes during zooming, of the i-th shaft upper surface interval di (i = 1, 2, 3,...) Counted from the enlargement side.

In this embodiment, a first unit (Gr1) having a negative power, a second unit (Gr2) having a positive power, and a second unit (Gr2) having a positive power are arranged in order from the enlargement side (projection side). 3 groups (Gr3)
The first lens unit (Gr1) and the second lens unit (Gr2) during zooming,
As shown by arrows m1 and m2, the zoom lens has a three-group configuration that moves in the optical axis (AX) direction. The third group (Gr3)
A dichroic prism (Pr) fixed at the time of zooming together with the third lens unit (Gr3) is arranged on the reduction side of.

In this embodiment, each group is configured as follows in order from the enlargement side. The first group (Gr1)
It comprises a negative meniscus lens concave on the reduction side, a positive meniscus lens convex on the reduction side, and a negative meniscus lens concave on the enlargement side. The second group (Gr2) includes a cemented lens of a biconcave lens and a biconvex lens, and a biconvex lens. The third group (Gr3) includes a first meniscus lens (M1) having a concave surface facing the enlargement side and having negative power, and a cemented lens including a biconvex lens and a biconcave lens, and
A second meniscus lens (M2) having a negative power with the convex surface facing the enlargement side in total, a biconcave lens, a positive meniscus lens convex on the reduction side, two biconvex lenses, and a positive positive lens on the enlargement side It consists of a meniscus lens and

As in this embodiment, there are three groups of negative, positive and positive in order from the magnification side, and the first group (Gr1) and the second group
In a zoom lens in which the group (Gr2) moves in the direction of the optical axis (AX), the third group (Gr3) includes a first meniscus lens having a negative power with a concave surface facing the enlargement side in order from the enlargement side. M1) and a second meniscus lens (M2) composed of a cemented lens composed of a biconvex lens and a biconcave lens, and having a positive or negative power with the convex surface facing the magnifying side in total.
And the third group (Gr3) further includes at least one negative lens on the reduction side with respect to the second meniscus lens (M2).
And at least one positive lens, and it is preferable that the first meniscus lens (M1) satisfies the following conditional expression (1). | (R _M1F + r _M1R ) / (r _M1F −r _M1R ) |> 3 (1) where r _{M1F is} the radius of curvature of the enlarged side surface of the first meniscus lens (M1), and r _{M1R is} the first meniscus lens (M1). ) Is the radius of curvature of the reduced side surface.

As described above, the third unit (G
r3), in order from the enlargement side, the first meniscus lens (M1) of negative power with the concave surface facing the enlargement side, and a biconvex / biconcave cemented lens, with the convex surface facing the enlargement side in total (in other words, By assembling a second meniscus lens (M2) of negative or positive power (with the concave surface facing the reduction side) and a negative lens and a positive lens disposed at least one each on the reduction side, astigmatism is reduced. can do. When this zoom lens is used, astigmatism can be suppressed even when the image circle is large as in a liquid crystal projector, so that an image of a display element whose size and pixel size have advanced can be projected with high image quality. .

The conditional expression (1) defines a condition range for favorably correcting spherical aberration and distortion. Therefore, when the value exceeds the conditional range of the conditional expression (1), spherical aberration and distortion are deteriorated. In addition, as the second meniscus lens (M2), a single lens having a positive or negative power with a convex surface facing the enlargement side may be used. When a positive meniscus lens is used as the second meniscus lens (M2), the positive power of the second meniscus lens (M2) should be weak.

Each of the groups constituting the above embodiment is constituted only by a refraction type lens which deflects an incident light beam by refraction, but is not limited to this. For example, each group may be constituted by a diffractive lens that deflects an incident light beam by diffraction, a refraction / diffraction hybrid lens that deflects an incident light beam by a combination of a diffraction action and a refraction action, or the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a zoom lens embodying the present invention will be described more specifically with reference to construction data, aberration diagrams, and the like. The example given here as an example
A lens configuration diagram (FIG. 1) corresponding to the embodiment described above and representing the embodiment shows the lens configuration of the present example. In the construction data of the present embodiment, ri (i = 1, 2, 3, ...) is the radius of curvature of the i-th surface counted from the enlargement side (i.e., the projection side), and Ri (i = 1, 2, 3, 3) , ...) is the effective diameter of the i-th surface counted from the enlargement side, di (i = 1,2,3, ...) is the i-th axial top surface count from the enlargement side, Ni (i = 1,2,
3, ...), νi (i = 1,2,3, ...) indicate the refractive index (Nd) and Abbe number (νd) of the i-th optical element with respect to the d-line counted from the magnification side. I have. In the construction data, the distance between the upper surfaces of the axes (variable distance) that changes due to zooming is the telephoto end.
(Long focal length end) [L] ~ Middle (intermediate focal length state) [M] ~
This is the axial distance between the groups at the wide-angle end (short focal length end) [S]. The focal length f and F number FNO of the entire system corresponding to each of these focal length states [L], [M], [S], and conditional expression (1)
Are also shown.

<< Construction Data of Example >> f = 70.3 to 62.0 to 54.0 FNO = 2.73 to 2.61 to 2.5 | (r _M1F + r _M1R ) / (r _M1F −r _M1R ) | = 3.36 [Radius of Curvature] [Effective Diameter] ] [Axis spacing] [Refractive index] [Abbe number] 1st group (Gr1)… r1 = 166.220 R1 = 32.50 d1 = 3.000 N1 = 1.61800 ν1 = 63.39 r2 = 53.294 R2 = 29.30 d2 = 11.500 r3 = -151.980 R3 = 29.20 d3 = 5.000 N2 = 1.80518 ν2 = 25.43 r4 = -77.955 R4 = 30.00 d4 = 5.000 r5 = -73.392 R5 = 29.00 d5 = 3.000 N3 = 1.61800 ν3 = 63.39 r6 = -378.550 R6 = 27.00 d6 = 15.000 to 26.214 ~ 40.285 Group 2 (Gr2) ... r7 = -266.234 R7 = 16.66 d7 = 2.500 N4 = 1.75520 ν4 = 27.51 r8 = 49.671 R8 = 18.12 d8 = 6.000 N5 = 1.75450 ν5 = 51.57 r9 = -105.763 R9 = 18.26 d9 = 0.300 r10 = 65.747 R10 = 18.49 d10 = 4.000 N6 = 1.75450 ν6 = 51.57 r11 = -491.096 R11 = 18.16 d11 = 12.539 to 7.936 to 3.500 Group 3 (Gr3) ... r12 = -100.291 R12 = 17.80 d12 = 7.500 N7 = 1.62280 ν7 = 56.88 r13 = -185.433 R13 = 17.26 d13 = 6.000 r14 = 123.958 R14 = 16.70 d14 = 5.000 N8 = 1.80741 ν8 = 31.59 r15 = -74.205 R15 = 18.00 d 15 = 2.000 N9 = 1.51680 ν9 = 64.20 r16 = 47.028 R16 = 17.00 d16 = 25.000 r17 = -37.672 R17 = 21.80 d17 = 3.000 N10 = 1.80518 ν10 = 25.43 r18 = 206.839 R18 = 25.00 d18 = 5.000 r19 = -259.684 R19 = 28.00 d19 = 7.000 N11 = 1.61800 ν11 = 63.39 r20 = -61.913 R20 = 27.00 d20 = 0.300 r21 = 1406.094 R21 = 31.00 d21 = 9.000 N12 = 1.61800 ν12 = 63.39 r22 = -70.000 R22 = 31.00 d22 = 0.300 r23 = 183.353 R23 = 33.00 d23 = 6.500 N13 = 1.61800 ν13 = 63.39 r24 = -191.249 R24 = 33.00 d24 = 0.300 r25 = 106.648 R25 = 33.00 d25 = 6.000 N14 = 1.61800 ν14 = 63.39 r26 = 265.332 R26 = 33.00 d26 = 5.000 Dichroic prism (r) ... r27 = ∞ R27 = 40.00 d27 = 41.200 N15 = 1.51680 ν15 = 64.20 r28 = ∞ R28 = 40.00

FIG. 2 shows an embodiment {dichroic prism
(Pr) and other aberrations of an object at infinity on the reduction side at the telephoto end [L] and the wide-angle end [S] (in order from the left, astigmatism such as spherical aberration). Y ′: image height). In the spherical aberration diagram, the solid line
(d) shows the spherical aberration with respect to the d-line, and the broken line (SC) shows the sine condition. In the astigmatism diagram, a broken line (DM) represents astigmatism with respect to the d-line on the meridional surface, and a solid line (DS) represents astigmatism with respect to the d-line on the sagittal surface. In the distortion diagrams, the solid line represents the distortion% with respect to the d-line. When the above embodiment is used as a projection zoom lens in a projection device (for example, a liquid crystal projector), the screen surface is originally an image surface and the display element surface (for example, a liquid crystal panel surface) is an object surface. In the embodiment, a reduction system (for example, an image pickup optical system) is used for optical design, and the optical performance is evaluated on the display element surface while considering the screen surface as the object surface.

[0017]

As described above, according to the present invention, since the zoom lens composed of negative, positive and positive lenses employs a lens configuration characteristic of the third lens group, various factors including astigmatism can be obtained. It is possible to realize a zoom lens in which aberration has been favorably corrected. Then, by using the zoom lens according to the present invention, it is possible to project an image of a display element whose size and size have been advanced with high image quality.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram of an embodiment (example).

FIG. 2 is an aberration diagram of an example.

[Explanation of symbols]

 Gr1 ... first group Gr2 ... second group Gr3 ... third group Pr ... dichroic prism AX ... optical axis

Claims (1)

[Claims] 1. A first group having negative power, a second group having positive power, and a third group having positive power are arranged in this order from the magnification side. And a zoom lens in which the second group moves in the optical axis direction. The third group includes, in order from the enlargement side, a first meniscus lens having a negative power with a concave surface facing the enlargement side, and a biconvex lens. A second meniscus lens having a positive or negative power and having a convex surface facing the magnifying side in total, and a third meniscus lens. A zoom lens comprising at least one negative lens and at least one positive lens on the reduction side, wherein the first meniscus lens satisfies the following conditional expression; | (r _M1F + R _M1R ) / (r _M1F -r _M1R ) |> 3, where r _{M1F is the} radius of curvature of the enlarged side surface of the first meniscus lens, and r _M1R is the radius of curvature of the reduced side surface of the first meniscus lens.