JPH03276113A - Projection lens - Google Patents

Abstract

PURPOSE:To obtain a wide-angle and compact lens which is very bright to have FNO <=1.0 and has a high image forming performance by constituting a lens system of five groups of five lenses and satisfying specific conditions. CONSTITUTION:The lens system consists of five groups of five lenses, namely, a first positive lens group, a second positive lens group, a third positive lens group having the strongest power of constituting lenses, a fourth negative lens group, and a fifth negative lens group which are arranged in order from the screen side. This lens system satisfies inequalities I to IV where (f), fi, ni, and hi are the resultant focal length of the whole of the system, the forcal length of the i-th lens group, the refractive index at 20 deg.C of the i-th lens group, and the average height of light on the paraxial tracking axis of the i-th lens group respectively and VTi=(ni-o)/(noi-n4oi) is true where noi and n4oi are the refrac tive index at 0 deg.C of the i-th lens group and that at 40 deg.C of the i-th lens group respectively.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection lens, particularly for a projector that has good optical performance, is wide-angle, compact, and very bright with F8°≦1.0. Regarding the projection lens.

[Prior Art] In recent years, projection televisions (abbreviated as PTVs) have been used not only for receiving television broadcasts, but also as display devices for electronic video equipment such as VTRs and video discs, and as computer output devices for displaying text, still images, etc. Demand for display use is increasing.

In order to make the image quality of PTV similar to that of direct-view television, improvements in brightness, contrast, resolution, etc. are desired, and in addition to performance, demands for compactness and cost reduction are increasing.

In particular, the image quality of PTV depends on the projection lens for the projector used, and the projection lens is required to have high imaging performance not only on the axis but also on the periphery.

In addition, making the lens unit of the projection lens more compact and reducing the cost of the lens itself have a great influence on making the PTV more compact and lowering the cost.

Traditionally, projection lenses have been made by combining a large number of glass lenses, but since only spherical lenses can be used with glass lenses, the number of lenses required increases, and the specific gravity of the glass material is also high, making it lighter. I couldn't figure it out.

However, recently, it has become possible to produce large-diameter aspherical plastic lenses with high precision and at low cost, so glass lenses and plastic lenses can be used together to make lenses more compact and lower in cost while maintaining optical performance. A projection lens is used.

[Problems to be Solved by the Invention] However, the linear expansion coefficient of plastic materials is significantly larger than that of optical glass, and the refractive index fluctuates greatly due to temperature changes.

For this reason, the plastic lens has a problem in that the back focus fluctuates greatly due to temperature changes, lowering the imaging performance and deteriorating the image quality of PTV.

Even among conventional projection lenses that use a combination of glass lenses and plastic lenses, there is no one that satisfies optical performance such as geometrical optical aberrations, is wide-angle, compact, and has a value of FNO≦10.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a projection lens that has good optical performance such as geometrical optical aberrations, is wide-angle and compact, and is extremely bright with FNO≦10. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides, in order from the screen side, a positive first group lens, a positive second group lens, and a positive third group lens having the strongest power among the constituent lenses. It has a five-element configuration in five groups, consisting of a negative fourth group lens, a negative fifth group lens with a concave surface with a strong curvature facing the screen side, and a first group lens, a second group lens, and a fourth group lens. The lenses each include at least one aspherical surface and are made of a resin material, where f: composite focal length of the entire system, fl; focal length of the first group lens, n,: of the first group lens. Refractive index of e -1ine at 200C hl: Average height of paraxial tracking light on the axis of the first group lens (however, = 1) nor: Refraction of e -1ine at O'C of the first group lens Rate n4Ql: e −1ine of the first group lens at 40'C
The projection lens was constructed to satisfy the refractive index condition.

[Production use] The above conditions will be explained below.

Condition (1) is for a large aperture lens such as the present invention.
This is a condition that limits the power of the two first group lenses and the second group lens, which mainly contribute to correction of spherical aberration and coma aberration.

The projection lens of the present invention is a projection lens for a projector that corresponds to the recent trend toward larger apertures, more compactness, and wider angles, and the two resin lenses of the first group lens and the second group lens include aspheric surfaces. As a result, the first group lens contributes to correcting the spherical aberration of light passing through a height of about 50 to 80% of the maximum lens aperture and the underlined coma aberration for off-axis light, and the second group lens contributes to correcting the underlined coma aberration for off-axis light. Contributes to correction of spherical aberration for light near the aperture.

When f 1 + f 2 becomes 30 or more, that is, when the power of the positive first group lens and the positive second group lens is weak,
As the beam diameter of the axial light incident on the positive third group lens increases, the spherical aberration generated in the third group lens inevitably increases, making it difficult for the entire system to correct the spherical aberration using other lenses. Getting worse.

On the other hand, when f 1 + f 2 becomes 10 or less, that is, when the powers of the first group lens and the second group lens become strong,
If any lens has an aspherical lens shape capable of correcting aberrations, either or both of the first group lens and the second group lens will become thicker, and the moldability of each lens will deteriorate.

In addition, in a lens system with normal optical aberrations corrected,
It becomes difficult to satisfy the temperature characteristics of condition (4).

Condition (2) is a condition regarding the focal length of the third group lens, which has a strong power in all lenses.

3. When `` is 1.3 or more, that is, when the power of the lens becomes weak, the power of other resin lenses becomes strong to obtain the prescribed focal length, making it impossible to satisfy condition (4), and aberrations also occur. Otherwise, the overall length of the lens becomes longer, which is contrary to compact design.

-4, when Eyu is less than 0.9, the spherical aberration and coma aberration generated by the third lens group increase, and cannot be corrected by the first, second, and fourth lens groups.

Condition (3) is a condition for the negative focal length of the fourth group lens.

The fourth group lens is a negative lens with relatively low power near the paraxial axis, but it corrects the back focus fluctuation due to temperature changes due to the first and second group lenses, and the aspherical surface allows the power of the lens periphery to be reduced. This lens corrects comatic aberration of the upper line of the off-axis light beam.

When f is 0 or more, condition (4), which is the temperature characteristic condition mainly for the first group lens, second group lens, fourth group lens, and fifth group lens, cannot be satisfied.

On the other hand, when f is -400 or less, spherical aberration for axial light increases.

Condition (4) is a condition for suppressing fluctuations in back focus caused by large changes in refractive index with respect to temperature changes in an optical system including a resin lens such as the present invention.

The back focus changes due to temperature changes due to heating of the CRT surface, which is undesirable.

[Implementation example] The present invention will be explained in detail below.

Here, r is the radius of curvature of each surface of the lens, d is the lens thickness or lens interval, and N is the refractive index of e -1ine of each lens.

In addition, the aspherical shape is a rotationally symmetric aspherical surface expressed as follows, where the apex paraxial curvature is 01, the conic constant is 1, and the aspherical coefficient is AI, in an orthogonal coordinate system with the optical axis direction as the X axis. .

(Example 1) FIG. 1 is a lens configuration diagram of a projection lens of this example, and FIGS. 2(a) to (C) are aberration diagrams thereof.

F No = 0.95 f = 95.3 Magnification = -0,1090580,696 100,112 500,923 -893,877 74,853 -260,085 -822,325 7,8Q0 42.155 500 7.500 27.000 6.000 5.267 1.49357 1.49357 1633 9357 0 -867.420 -45.532 63.729 000 6 ,500 1 1st side -0,188355X 10-' O,194021X 10-" -0,322359X 10-" 0.687992X 10-" Third surface O A x -0,258063X 10-'1.493
57 1.53740 (CRT face plate) 2nd surface -0,242141X 10-' -0,120931X 10-' 〇10,287164X 10-" 0.733197X 10s6 4th surface 0.360645X 10-' - 0,317321X 10-' 0.202032X 10-7 -0.631183X 10-" -0,131014X 10-1" 0.302844X 10-" 7th side 0.343336X 10'-' -0,390638X 10-" -0.442881 8th side 0.415713X 10-' 0.137529X 10-" 0.682198X 10-12 0.195992xlO-" 0.778382X 10-' -0,408718X 10-' 0.322625X 10-" -0,118725x 10 -" (Example 2) Figure 3 is a lens configuration diagram of the projection lens of this example,
Figures (a) to (C) are aberration diagrams thereof.

F NO = 0.95 f = 95.7 Magnification = -0,10905369,305 -296,272 6,000 24,00O 1,49154 1 12 -106.418 -98.389 85.870 -164.834 213 .326 -156.908 -42.230 42.230 7.800 21.647 29.000 6.000 4.5θ0 58.974 3,500 8.000 6.500 1st surface -0,828121X 10-' -0.732041

0.562819x 10-" -0,643811X 10-17 Third surface -0,724574X 10-' 0.108286x ICr' -0,291448X 10-' 0.369438X 10-' -0,522349X 10-12 0. 204,056 ' -0,442078X 10-' 0.329159X 10-' 8th side -0,477544X 10-' 0.151784X 10-' 9th side 1 -0.399177X 10-' -0,105023X 10-' 0. 782171X 10-" -0.222721X 10-" -0,987743X 10-' -0,571591X 10-12 0.183110X 10-" 10th side -08 A, OA, OA, OA, OA, O A, O A, O 1o0 (Example 3) Fig. 5 is a lens configuration diagram of the projection lens of this example, and Fig. 6
Figures (a) to (c) are aberration diagrams thereof.

1 2 FN0=0 5 85.742 107.458 121.602 234.597 92.544 -150.207 1066.899 961.361 -38.710 -38.710 f=95 Magnification = -0,10905 6,500 30,000 8,500 19,166 25,337 16,000 000 50,878 3,500 8,000 6,50O 1,49357 9357 1633 9357 1,49357 1,43664 (liquid) 1.53740 (CRT face plate) Front page 0 -0.457592X 10-' -0,163138X 10-” -0,184501X 10’-” O, 450640X 10-16 Third page -0,4?0357X 10-' 0.286428X 10-' -0,128893x 10-' 0.135551X 10-” -0,267528X 10-” 2nd side 0.229719X 10-' -0,273857x 10-' -0,137596X 10s2 0.432234X 10-” 4th page 0.406233X 10-I+ 10, 856301X 10-' 0.288866X 10-” -0,663138X 10-@ 0.755931X 10s3 A.

A. 0.285353X 10-” 7th side -0,734390X 10-' 0.226403X 10-' -0,174111X 10-” 0.498936X 10-16 9th page 1 0.315945X 10-' -0,240892X 10-” A.

A□. -0,662717X 10-173 4 s 6 10th side 0.7 A, OA, OA, 0.162012X 10 s 1 A, O
A9 OA, O Al. -0,463427x 10-”A,
. 0 (Example 4) FIG. 7 is a lens configuration diagram of the projection lens of this example.
Figures (a) to (C) are aberration diagrams thereof.

F N0 = 0.95 f = 96.8 Magnification = -0,11111111,961 341,133 -243,683 -163,351 81,655 -170,686 9,000 31,226 10,000 500 28,000 766 1,49357 1,49357 1,51633 -410,629 2328,424 -38,172 -38,172 1 0 2 1st side -0, 739734X 10-' 0.491405X 10s 0 -0.290101X 10- ]2 0.583574X 10-" 00 10 00 00 00 1.49357 1.49357 1.43664 (Liquid) 1.53740 (CRT face plate) 2nd surface -0,231780X 10-' -0,944666X 10-10 0.186976 -0.363971X 10-16 7th surface 0.453720X 10-' -0,202955X 10-" 0, 276589 X 10-" 4th surface 3 A.

s 6 A.

8 9 A1゜ 0.106636X 10-' -0,160179X 10-' 0.811741X 10-' -0,221770X 10-” 0.155113X 10-” -O, 107308X 10-” 8th page 0.517961X 10 bows -0,202955X 10-” 0.276589X 10-” A.

-0,136395X 10-" A1゜-0,136395X 10-"9th surface 1 0.712268X 10"" -0,202086x 10-' O,108253 ) FIG. 9 is a lens configuration diagram of the projection lens of this example.
0 (a) to (C) are respective aberration diagrams.

F No = 0.98 f = 97.8 Magnification = -0,111111 3 4 89,397 133,956 1847,931 -284,466 68,375 -176,141 -67,473 -145,525 -59, 786 1st side - 0,421799X 10-' 12.000 45.000 7.000 10.000 28.000 12.000 5.800 53.192 e, oo.

5, 750 A.

4 Engineering 9357 1.49357 1.51633 1.49357 1.51633 1.53740 (CRT face plate) 2nd surface -0,103306X 10-' -0,307943X 10-" -0,102146X 10-" 0.300901X 10-" 3rd side 0.258171X 10-' -0,126368X 10'-' 0.958379x 10-7 -0.271976X 10-' 0.61?276X 10-" 0.923867X 10-" 7th side -0,556825X 10-' 0.368368X 10-'s 3 0.131311x 10-" 4th side 0.336623X 10-' -0,340649X 10-' 0.156182X 10-' -0,341843X 10-" 0 .664800X 10"" 0.918470X 10-" A on the 8th side, OA11O A, 0.521323x 10-' A 4
0.610109x 10-'A5 0
A, OA a -0,27
2657X 10-” A e -0,2588
18X 10-”A, OA, OA*0.840512X 10-”A s
0.902711X 10-”Am OAm
O A +o -0,100813X 10-" A
so -0,913978 There is little variation in the image quality, the imaging performance is extremely high, and the optical performance such as geometrical optical aberrations is good.

[Brief explanation of drawings]

FIGS. 1, 3, 5, 7, and 9 are lens configuration diagrams showing projection lenses of Examples 1 to 5 of the present invention, and FIGS. 2(a), (b), and ( C), Figure 4(a)
, (b) and (C), Figure 6 (a), (b) and (
C), Figures 6(a), (b) and (C), Figure 8(a)
), (b) and (C) and Figure 10 (a), (b)
and (C) are respectively a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram of each projection lens of Examples 1 to 5 of the present invention.

Claims (1)

[Claims] In order from the screen side, a positive first group lens, a positive second group lens, a positive third group lens with the strongest power among the constituent lenses, a negative fourth group lens, and a curvature toward the screen side. It consists of five elements in five groups, consisting of a negative fifth group lens with a strongly concave surface, as well as a first group lens, a second group lens, and a fourth group lens.
Each group lens includes at least one aspherical surface and is made of a resin material, and (1) 10<(f_1+f_2)/f<30(2)0.
9<f_3/f<1.3 (3)-400<f_4/f<0 (4)▲Mathematical formulas, chemical formulas, tables, etc.▼Where, f: Composite focal length of the entire system f_i: i-th group lens Focal length n_i; Refractive index of e-line at 20°C of the i-th group lens h_i; Average height of paraxial tracking light on the i-th group lens (however, h_1=1) V_T_i=(n_i-0) /(n_o_i-n_4_
0_i) n_0_i; e-li of the i-th group lens at 0°C
refractive index of ne n_4_0_i; e-lin of i-th group lens at 40°C
A projection lens characterized in that it satisfies a refractive index condition of e.