JPH0815607A - Projection lens - Google Patents

Abstract

PURPOSE:To provide a wide-angle, compact and very bright projection lens having excellent optical performance, a small number of lenses and FNO=0.95. CONSTITUTION:This lens is composed of three groups three-lens constitution, in order from a screen side, of a first group lens L1 whose at least one surface is aspherical surface and made of glass or resin, a second group lens L2 whose at least one surface is aspherical surface, made of glass and having an intensive positive power and a third group lens L3 having an intensive concave surface confronting the screen side and made of glass or resin. The conditions: 1.0<=f2/<=1.2, 1.5<=T1MAX/T1MIN<=2.5 are satisfied, where f2 is the focal distance of the second group lens, (f) is the focal distance of the whole system, T1MAX is the maximum value of the thickness of the first group lens L1 and T1MIN is the minimum value of the thickness of the first group lens L1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens, and more particularly to a projector device for enlarging a CRT image, which has excellent optical performance, is wide-angle and compact, and has a very bright FNO = 0.95. Regarding the projection lens.

[0002]

2. Description of the Related Art In general, a projector device is widely used not only for receiving television broadcast images but also as a display for electronic image devices such as VTRs and LDs, and as a display for a computer output device for displaying characters and still images. . In addition, recently, demand for high-definition output devices such as high-definition video is also increasing. Therefore, it is very important for the projection lens used in the projector device to have good performance such as resolving power, and since the enlargement magnification is also large, the F value must be made extremely small, and further, Compact system,
Since cost reduction is also important, widening the angle of the projection lens and reducing the number of lenses have become issues.

Conventionally, as a projection lens, for example, a five-group, five-element structure disclosed in JP-A-63-139312, JP-A-55-124114, and JP-A-60-208720. There is a three-group / three-element configuration disclosed in, for example.

[0004]

However, none of the conventional projection lenses satisfy all of the above-mentioned problems. For example, a wide-angle lens (angle of view 63 °) as disclosed in Japanese Patent Laid-Open No. 63-139312 is used. With a bright (FNO = 1.0) lens, the number of lenses in the 5 groups is increased to 5 lenses. On the other hand, in a lens system with a small number of lens elements of 3 groups and 3 elements,
JP-A-55-124114 and JP-A-60-208
As described in Japanese Patent No. 720, etc., the angle of view 54 °, FNO
= 1.1, the angle of view is narrow and the brightness is also dark. Further, although the aberration correction is improved by making the second lens group aspherical, when this lens is a resin lens, the performance due to temperature change is extremely large.

The present invention has been made in view of the above problems of the prior art, and has excellent optical performance, a wide angle and compact size, a small number of lenses, a very bright FNO = 0.95, and a temperature. It is an object of the present invention to provide a projection lens with less performance deterioration due to changes.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a projection lens in order from the screen side.
A first group lens having at least one aspherical surface made of glass or resin, a second group lens having at least one aspherical surface made of glass with strong positive power, and a surface facing the screen side. Third group 3 which is a strong concave aspherical surface and is composed of a third group lens made of glass or resin
1.0≤f2 / f≤1.2 1.5≤T1 MAX / T1 MIN ≤2.5 where f2 is the focal length of the second lens group, and f is the focal length of the entire system. T1 MAX: The maximum thickness of the first lens group T1 MIN: The minimum thickness of the first lens group is satisfied. Here, the thickness of the lens means the shortest distance through which one surface of the lens can pass and the other surface can be referred to.

[0007]

The operation will be described below based on the projection lens of the present invention shown in FIG. In FIG. 1, the first lens unit L1 is a glass lens having an aspherical surface on the r1 surface and a spherical surface on the r2 surface.
It is constructed so as to satisfy ≤T1 MAX / T1 MIN ≤2.5. In the second lens unit L2, the r3 surface is an aspherical surface, and the r4 surface is
It is a glass lens with a spherical surface, and 1.0≤f2 / f≤
It is configured to satisfy 1.2. The third lens unit L3 is an aspherical resin lens whose r5 surface has a strong concave surface facing the screen. LQ is the third lens group L3 and CR
It is a liquid between the T face plate FP (glass substrate) and has an effect as a negative lens in combination with the third lens group L3 and also has an effect of cooling the heat generated from the CRT. The first lens group L1 may be a resin lens and the third lens group L3 may be a glass lens.

As an optical action, the first lens unit L1 has at least one aspherical surface, which mainly contributes to aberration correction of off-axis rays. However, T1 MAX / T1 MIN
When <1.5, the power of the first lens unit L1 itself becomes weak, and the coma of a light beam having a large angle of view becomes large, which makes correction difficult. On the other hand, when 2.5 <T1 MAX / T1 MIN, the spherical aberration by the first lens unit L1 increases and it becomes difficult to correct, or it becomes difficult to obtain a bright lens with a small FNO.

The second lens unit L2 is a lens that bears most of the focal length of the entire system, and has at least one aspherical surface, which mainly contributes to correction of spherical aberration. When the power of the second lens group L2 is too strong,
That is, when f2 / f <1.0, the spherical aberration and coma generated by the lens L2 increase, and it becomes difficult to correct aberrations in this lens L2 and the other lenses L1 and L3. On the other hand, when the power of the second lens group L2 is too weak, that is, 1.2 <f2 / f, not only does the total lens length increase, which is contrary to compactness, but the power of the first lens group L1 increases and the overall power increases. It becomes difficult to correct the aberration. In recent years, glass aspherical surface processing technology has made remarkable progress, and as methods for manufacturing aspherical glass lenses, there are precision grinding processing and polishing, or molding with a glass mold, which makes it possible to produce large-diameter aspherical surfaces with high accuracy. ing.

The third lens unit L3 is a negative lens having a strong concave surface on the screen side. Since it is a wide-angle lens, the third lens unit L3 is an aspherical lens, which mainly corrects field curvature and also contributes to coma aberration correction. ing.

[0011]

EXAMPLES Examples 1 to 5 of the present invention will be described below. Here, r is the radius of curvature of each surface of the lens, d is the lens thickness or lens interval, and m is the material of each lens.

Further, the aspherical shape is expressed by the formulas 1 and 2 where C is the paraxial curvature of the vertex, K is the conic constant, and Ai is the aspherical coefficient in an orthogonal coordinate system with the optical axis direction as the X axis. It is a rotationally symmetric aspherical surface represented.

[0013]

[Equation 1]

[0014]

[Equation 2]

[0015]

Example 1 FIG. 1 is a lens configuration diagram showing a projection lens of this example, and FIGS. 2A to 2C are aberration diagrams of the projection lens of this example.

FNO = 0.95 f = 76.21 mm Magnification = −0.1044 Half angle of view: 36.0 ° f2 / f = 1.13 T1 MAX / T1 MIN = 2.07 rd m 1 60.34 9.00 BK7 2 134.76 25.50 3 92.79 25.00 BK7 4 −78.43 43.82 5 −32.01 3.20 PMMA 6 −35.50 5.00 LQ (liquid) 7 ∞ 10.30 FP (CRT face plate) 8 ∞ 1st surface 3rd surface K 0 K 0 A4 -0.6623E-06 A4 -0.8921E-06 A6 -0.8923E-09 A6 0.9421E-09 A80 .4612E-12 A8 -0.5402E-12 A10 -0.2318E-15 A10 0.1083E-15 5th surface 6th surface K-0.1189E + 01 K -0.5000E + 00 A4-0 1519E-05 A4 0 A6 -0.1836E-08 A6 0 A8 -0.9768E-12 A8 0 A10 0.6345E-15 A10 0

[0017]

Example 2 FIG. 3 is a lens configuration diagram showing a projection lens of this example, and FIGS. 4A to 4C are aberration diagrams of the projection lens of this example.

FNO = 0.95 f = 79.07 mm Magnification = −0.1061 Half angle of view: 35.1 ° f2 / f = 1.13 T1 MAX / T1 MIN = 2.02 rd m 1 67.79 12.00 BK7 2 176.65 30.00 3 94.35 25.80 BK7 4 -82.06 44.56 5 -38.06 5.00 BK7 6 ∞ 3.00 LQ (liquid) 7 ∞ 10.30 FP (CRT face plate) 8 ∞ 1st surface 2nd surface K 0 K 0 A4-0.8678E-06 A4-0.3817E-07 A6 0.3674E-09 A6 0.2128E-09 A8-0.6522E- 12 A8 -0.5178E-12 A10 0.1367E-15 A10 0.1658E-15 Third surface Fourth surface K0 K0 A4 -0.4246E-06 A4 0.3237E-06 A6 0.1 43E-09 A6 -0.1125E-09 A8 -0.7075E-13 A8 0.1135E-14 A10 -0.2285E-16 A10 -0.1713E-16 Fifth surface K -0.1189E + 01 A4 -0.1021E -05 A6 -0.1744E-08 A8 0.6241E-12 A10 0.1192E-16

[0019]

[Embodiment 3] FIG. 5 is a lens configuration diagram showing a projection lens of the present embodiment, and FIGS. 6A to 6C are aberration diagrams of the projection lens of the present embodiment.

FNO = 0.95 f = 81.25 mm Magnification = −0.1059 Half angle of view: 34.5 ° f2 / f = 1.16 T1 MAX / T1 MIN = 2.35 rd m 1 66.20 12.00 BK7 2 181.91 30.00 3 101.74 25.80 BK7 4 -85.91 44.92 5 -37.05 BK7 6 -55.00 5.00 LQ (liquid) 7 ∞ 10.30 FP (CRT face plate) 8 ∞ First surface Second surface K 0 K 0 A4 -0.9453E-06 A4 -0.1009E-06 A6 0.7243E-09 A6 0.5307E-09 A8-0 8764E-12 A8 -0.7433E-12 A10 0.1729E-15 A10 0.2031E-15 Third surface Fourth surface K0K -0.1189E + 01 A4 -0.6395E-06 A4 -0.1475E-05 A6 0.3693E-09 A6 -0.1040E-08 A8 -0.2670E-12 A8 0.2262E-12 A10 0.6961E-16 A10 0.7628E-16

[0021]

[Embodiment 4] FIG. 7 is a lens configuration diagram showing a projection lens of the present embodiment, and FIGS. 8A to 8C are aberration diagrams of the projection lens of the present embodiment.

FNO = 0.95 f = 83.15 mm Magnification = −0.1071 Half angle of view: 35.2 ° f2 / f = 1.08 T1 MAX / T1 MIN = 1.72 rd m 1 75.30 8.10 PMMA 2 144.80 30.78 3 92.51 30.00 BK7 4 -82.62 50.99 5 -62.19 3.20 PMMA 6 -65.00 5.00 LQ (liquid) 7 ∞ 14.10 FP (CRT face plate) 8 -350.00 1st surface 2nd surface K0 K0 A4-0.4829E-06 A4 0.1343E-06 A6 0.1870E-09 A6 0.5564E-09 A8 -0.2360E-12 A8 -0.4166E-12 A10 0.8231E-17 A10 0.8776E-16 3rd surface 4th surface K0 K0 A4 -0.6231E-06 A4 0.10 9E-06 A6 0.5896E-09 A6 0.2126E-09 A8 -0.3515E-12 A8 -0.1535E-12 A10 0.6648E-16 A10 0.3205E-16 5th surface 6th surface K-0 1000E + 01 K -0.2000E + 01 A4 -0.2677E-05 A4 -0.2100E-05 A6 -0.1031E-08 A6 -0.9300E-09 A8 0.1368E-12 A8 0.2300E-12 A10 0. 5274E-16 A10 -0.1200E-16

[0023]

Embodiment 5 FIG. 9 is a lens configuration diagram showing a projection lens of this embodiment, and FIGS. 10A to 10C are aberration diagrams of the projection lens of this embodiment.

FNO = 0.95 f = 86.69 mm Magnification = −0.1055 Half angle of view: 33.4 ° f2 / f = 1.11 T1 MAX / T1 MIN = 2.04 rd m 1 91.24 8.50 PMMA 2 275.69 31.66 3 102.62 31.00 BK7 4 -86.95 52.09 5 -51.82 3.20 PMMA 6 -65.00 5.00 LQ (liquid) 7 ∞ 14.10 FP (CRT face plate) 8-350.00 1st surface 2nd surface K0 K0 A4 0.1831E-06 A4 0.8969E-06 A6 -0.1101E-08 A6 -0.1093E-08 A8 0.7506E-12 A8 0.8181E-12 A10 -0.1704E-15 A10 -0.1655E-15 4th surface 5th surface K0K -0.1000E + 01 A4 0.359 E-06 A4 -0.3255E -06 A6 -0.9626E-10 A6 -0.4505E-08 A8 0.3945E-13 A8 0.2510E-11 A10 -0.6483E-17 A10 -0.5209E-15 6th surface K-0.2000E + 01 A4 -0.2100E-05 A6 -0.9300E-09 A8 0.2300E-12 A10 -0.1200E-16

[0025]

As described above, according to the projection lens of the present invention, although it is composed of 3 elements in 3 groups, it is wide-angle and compact, it is very bright with FNO = 0.95, and the performance deterioration due to temperature change is small. A projection lens for a projector device having good optical performance can be obtained.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram showing a projection lens of Example 1 of the present invention.

2A and 2B are diagrams showing the optical performance of the projection lens in Example 1 of the present invention, where FIG. 2A is a spherical aberration diagram, FIG. 2B is an astigmatism diagram,
(C) is a distortion diagram.

FIG. 3 is a lens configuration diagram showing a projection lens of Example 2 of the present invention.

4A and 4B are diagrams showing the optical performance of the projection lens of Example 2 of the present invention, in which FIG. 4A is a spherical aberration diagram, and FIG. 4B is an astigmatism diagram;
(C) is a distortion diagram.

FIG. 5 is a lens configuration diagram showing a projection lens of Example 3 of the present invention.

6A and 6B are diagrams showing the optical performance of the projection lens of Example 3 of the present invention, where FIG. 6A is a spherical aberration diagram, and FIG. 6B is an astigmatism diagram;
(C) is a distortion diagram.

FIG. 7 is a lens configuration diagram showing a projection lens of Example 4 of the present invention.

8A and 8B are diagrams showing the optical performance of the projection lens in Example 4 of the present invention, in which FIG. 8A is a spherical aberration diagram, FIG. 8B is an astigmatism diagram,
(C) is a distortion diagram.

FIG. 9 is a lens configuration diagram showing a projection lens of Example 5 of the present invention.

FIG. 10 is a diagram showing the optical performance of the projection lens of Example 5 of the present invention, (a) is a spherical aberration diagram, (b) is an astigmatism diagram,
(C) is a distortion diagram.

[Explanation of symbols]

 L1 first lens group L2 second lens group L3 third lens group

Claims (1)

[Claims] 1. A first lens group, at least one surface of which is aspherical and made of glass or resin, and a second lens group of at least one aspherical surface, which is made of glass and has a strong positive power, in order from the screen side. A lens system of three-group, three-lens structure including a lens and a third lens group made of glass or resin, which is a strongly concave aspherical surface facing the screen, and 1.0≤f2 / f ≤1.2 1.5 ≤T1 MAX / T1 MIN ≤2.5 where f2; focal length of second lens group f; focal length of entire system T1 MAX; maximum thickness of first lens group T1 MIN A projection lens satisfying the minimum value of the wall thickness of the first lens group.