JPH02208618A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a large aperture ratio and a high power variation ratio and to obtain high optical performance where aberrations are compensated excellently over the entire power variation range by specifying the lens constitution of respective lens groups. CONSTITUTION:A 5th lens group consists of two lens groups, i.e. a 51st group and a 52nd group, and inequalities I-IV hold, where Ri, j is the radius of curvature of a (j)th lens surface of an (i)th group, fi the focal distance of the (i)th group, f51 and f52 the focal distances of the 51th and 52nd groups, Ni, j and nui, j the refractive index and Abbe number of the material of the (j)th lens of the (i)th group, Di, j the center thickness or air gap of the (j)th lens of the (i)th group and NA the mean refractive index of the materials of the 511th and 512th lenses in the 5th group. Consequently, the large aperture ratio and high power variation are obtained while the high optical performance is maintained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a zoom lens, in particular a zoom lens with a large aperture ratio of F number 1.2, a high zoom ratio of about 10, and a zoom lens that covers the entire zoom range. The present invention relates to a zoom lens that has good optical performance and is suitable for photographic cameras, video cameras, and the like.

(Prior Art) Photographic cameras, video cameras, and the like have traditionally required zoom lenses with large apertures, high zoom ratios, and high optical performance.

Among these, in zoom lenses for consumer video cameras, due to the increase in the number of pixels of image sensors such as CCDs, for example from 250,000 pixels to 330,000 pixels, the spatial frequency is approximately 50 lines/l1lIn over the entire screen. High resolution is required.

A zoom lens with a variable power ratio of about 10 is available, for example,
This method has been proposed in Japanese Patent Laid-Open No. 17042, Japanese Patent Laid-Open No. 54-23556, etc. The publication describes, in order from the object side, a first group with positive refractive power for focusing, a second group with negative refractive power for zooming, a third group for correcting the image plane that changes due to zooming, and a second group with negative refractive power for zooming. We have proposed a so-called five-group zoom lens having five lens groups: a fourth group for converting the light beam from the third group into an afocal light beam, and a fifth group for imaging.

In general, in order to maintain high optical performance in a 5-group zoom lens and achieve a large aperture ratio and high zoom ratio, it is important to appropriately set the optical constants of each lens group that makes up the lens system. I'm coming.

For example, if you simply strengthen the refractive power of each lens group or increase the number of lenses to achieve a large aperture ratio and high zoom ratio, the entire lens system will become larger, and spherical aberration at the center of the screen and coma aberration toward the periphery of the screen will occur. Many higher-order aberrations such as sagittal halo aberrations and sagittal halo aberrations occur, and aberration fluctuations also increase during zooming, making it difficult to obtain high optical performance.

On the other hand, the surface of the cover glass and the surface of the image sensor in COD, MOS, etc., which are currently widely used as image sensors in video cameras, generally have high reflectance, and therefore the light reflected from these surfaces is reflected on the lens surface of the photographic lens. The light is reflected by the camera, lens barrel, etc., and re-enters the image sensor, causing so-called ghost and flare.

As described above, there are various requirements for photographic lenses used in video cameras, such as having good optical performance and not generating harmful light such as ghosts or flares.

(Problems to be Solved by the Invention) The present invention provides an aperture ratio of F/1.
It has a large aperture of about 2 and a high zoom ratio of 10, and has high optical performance over the entire zoom range. When applied to video cameras, etc., it prevents ghosts and flares due to light reflected from the image sensor surface. The purpose of the present invention is to provide a compact zoom lens that prevents the occurrence of.

(Means for Solving the Problems) The zoom lens according to the present invention includes, in order from the object side, a first group having a positive refractive power for focusing, a second group having a negative refractive power having a variable power function, and a second group having a negative refractive power having a variable power function. A third group with negative refractive power that corrects the image plane that changes depending on the magnification, a fourth group with positive refractive power that emits the divergent light beam from the third group in a divergent state, and a fourth group that has an imaging function. The fifth lens group has two lens groups, a 51st group and a 52nd group, and the 1st group has a negative meniscus shape with a convex surface facing the object side. The 11th lens group consists of a bonded lens in which the 12th lens has a convex surface, and the 13th lens has a positive meniscus shape with the convex surface facing the object side. The third group consists of a bonded lens in which a meniscus-shaped 21st lens surface is a concave negative 22nd lens and a positive 23rd lens, and both lens surfaces are a concave negative 31st lens and a positive 23rd lens. The fourth group consists of a positive 41st lens whose both lens surfaces are convex,
The 51st group includes a 511th lens with a strong refractive surface facing the object side and both lens surfaces having convex surfaces, a 512th lens with a strong refractive surface facing the object side and both lens surfaces having convex surfaces, and a 512th lens with a strong refractive surface facing the object side. The 52nd lens group consists of four lenses: a negative 513th lens with a concave surface facing the object side, and a positive 514th lens with a convex strong refractive surface facing the object side, and the 52nd lens group has a concave strong refractive surface facing the image side. The negative 521st lens surface is a convex 522nd lens, and the positive 52nd lens has a convex strong refractive surface facing the object side.
The radius of curvature of the j-th lens surface of the i-th group is Ri, j, the focal length of the i-th group is fi, and the focal lengths of the 51st and 52nd groups are respectively f51. f52, the refractive index and Atsube number of the material of the j-th lens of the i-th group are respectively Ni
, j, νi, j, the center thickness or air gap of the j-th lens of the i-th group is Di, j, and the average refractive index of the material of the 511th lens and the 512th lens is NA...・・・・・・・・・・・・(1) ・・・・・・・・・・・・(2) ・・・・・・・・・・・・(3) ・・・・・・・・・・・・(4) 0.3<D5. B/f5 <0.4 -----
(5) It is characterized by satisfying the following condition.

(Example) FIG. 1 is a cross-sectional view of a lens at the wide-angle end zoom position of Numerical Example 1 of the present invention. In the figure, the symbol is the first group with positive refractive power for focusing, ■ is the second group with negative refractive power that moves monotonically for zooming, and m is the lens for correcting the image plane that changes with zooming. a third group with negative refractive power that moves with a convex trajectory toward the object side;
(2) is the fourth group with positive refractive power that allows the divergent light flux from the third group to exit in a diverging state; (2) is the fifth group that has a fixed imaging function; and V-1 is the 51st group. group, V-2 is the fifth
The second group, SP, is a fixed aperture.

In this example, in such a zoom type, the lens configuration of each lens group from the first group to the fifth group is specified as described above, and the large aperture ratio is achieved by satisfying conditional expressions (1) to (5). Aberrations associated with high zoom ratios and high zoom ratios are well corrected to achieve high optical performance over the entire zoom range.

In particular, aberrations associated with large aperture ratios, such as spherical aberration, astigmatism, and chromatic aberration, are well corrected by appropriately setting the lens shape, material refractive index, and dispersion of each lens in the fifth group. .

In addition, residual aberrations in the variable power system, such as spherical aberration and comatic aberration, are corrected in a well-balanced manner.

Furthermore, by setting the refractive power of the fourth group so that the diverging light flux from the third group exits in a diverging state, the reflected light flux from the image sensor or filter is reflected on any lens surface and re-enters the image sensor. This effectively prevents ghosts, flares, etc. from occurring.

Next, the technical meaning of each of the above conditional expressions will be explained.

Conditional expression (+) corresponds to the sum of the refractive powers of the object-side lens surfaces of both the 511th lens and the 512th lens. If the upper limit is exceeded and the refractive power becomes too weak, a lot of coma flare will occur, and if the lower limit is exceeded, the residual amount of annular spherical aberration will increase, which is not good.

Conditional expression (2) relates to the refractive power of the lens surface on the image plane side of the negative 513th lens with its concave surface facing the object side. If the upper limit is exceeded and the refractive power becomes too strong, a lot of high-order spherical aberration will occur, and if the lower limit is exceeded and the refractive power becomes too weak, the light reflected from the imaging surface will be reflected by this lens surface and the image will not be captured. This is not a good idea because the image is re-formed near the surface and ghosts and flares are more likely to occur.

Conditional expression (3) relates to the refractive power of the object-side lens surface of the 523rd lens, and is mainly intended to satisfactorily correct distortion and field curvature. If the upper limit is exceeded and the refractive power becomes too weak, the negative distortion will become too large on the wide-angle side, and if the lower limit is exceeded and the refractive power becomes too strong, the amount of curvature of the meridional image surface will increase, so this is not recommended. do not have.

Conditional expression (4) is used to appropriately set the difference between the average value of the Abbe numbers of the two positive lenses in the 52nd lens group and the Abbe number of the negative lens, and to satisfactorily correct chromatic aberration. If the difference in Abbe numbers becomes too large beyond the upper limit, axial and lateral chromatic aberrations will be overcorrected, resulting in a decrease in resolution. If the lower limit is exceeded, axial and lateral chromatic aberrations will be insufficiently corrected, causing color blurring to occur at the periphery of the screen, which is undesirable, as it will degrade image quality.

Conditional expression (5) sets the air spacing between the 51st and 52nd groups, which are divided into two groups based on the widest air spacing in the 5th group, to achieve a good balance between axial aberrations and off-axis aberrations. This is for correction.

If the air gap becomes too wide beyond the upper limit, the overall length of the fifth lens group increases and it becomes difficult to satisfactorily correct axial aberrations such as spherical aberration. If the air gap becomes too narrow beyond the lower limit, spherical aberration will be overcorrected and it will become difficult to correct off-axis aberrations such as astigmatism and coma in a well-balanced manner.

In this embodiment, a refractive surface that is stronger toward the object side means that it is stronger than other lens surfaces, that is, the lens surface that is closer to the image plane.

Next, numerical examples of the present invention will be shown. In numerical examples R
i is the radius of curvature of the i-th lens surface in order from the object side, D
i is the i-th lens thickness and air distance from the object side, Ni
and νi are the refractive index and Abbe number of the glass of the i-th lens, respectively, in order from the object side. Note that R31 and R32 are glass blocks such as a face plate of an image sensor.

Furthermore, Table 1 shows the relationship between each of the above-mentioned conditional expressions and the word values in the numerical examples.

Numerical Example 1 F-1~9.38 R1 14.793 R2-5,846 R3--15,311 R4-4,891 R5= 10.825 11 6- 16.38O R7~ 1.876 R8- -2,246 R9-2,247 RIG -18,91O R11--3,678 1H2-4,372 8+3- 63.754 Ri4- 7.323 R5--3,863 Old 6I-Aperture Ri7- 8. 037 Ri8 -20,698 Ri9- 4.395 FNoi: 1.25 2 (Ll-5+, 3' ~
5.9'~1.75 D I-0,284N 1-1.80518 ν
1-25.40 2- 1.056 N 2-
1.60311 ν 2-60.70 3- 0.0
22 D 4- 0.556 N 3-1.6968
0 ν 3-55.5D5・Variable D 6- 0.125 N 4-1.8340
0 υ 4 37, 2D7 0.537 D B-0,102N S-1,71299ν 5
-53.809-0.397 N 6 palanquins 1.8466
6 ν 6-23.9010-variable DI=0.136 N 7-1.7+999 v
7-50.3012-〇, 295 N 8-1.
80518 ν 8@25.4D3・Variable D 4- 0.636 8 9-1.60311
υ 9-60.7DI5- 0.113 016- 0.227 017-0.397 NIO mati 1.589+3
SI10-61.2DI8- 0.017 019 禦 0.511 Ni! -1,58913 sill-61.2R20--16,9B9 R21--3,553 R22-16,193 R23rd 2.546 R24th -25,020 825-249,278 R26-1,647 827-4 ,990 R28--3,779 R29-2,003 R30-32,532 R31=o.

R32-■ 020- 0.255 021- 0.170 N+2-1.84666
v12=23.9D22- 0.017 D23= 0.715 N13m1.60311
v13-60.7024- 1.230 D25-0.102 N+4-1.74950
C14-35.3026- 0.147 027- 0.295 N+5-1.62299
ν15・58.1028@0.017 D29" 0.383 N+6-1.59551
v16-39.2[130-0,5[18 03t=Q,68t N17-1.51633
v 17”64.1 Numerical Example 2 F-1 ~ 9.38 RIO Rumor R11 Maro I2- I5- I6- 14.793 5.846 -15.311 4.891 10.825 16.380 1.878 - 2.246 2.247 -18.910 -3.676 4.372 63.754 7.323 -3.863 Aperture 7.919 -22.634 4.330 -16.765 FNo-1:1.25 2ω1151 .3' ~
5.9'~1.75 DI=0.284 N 1-1.805
+8 v 1-25.48 2- 1.056
N 2-1.60311 ν 2-60.7[1
3-0,022 D 4- 0.556 8 3-1.89680
v 3-55.5D5・Variable D B-0, 12584-1, 83400v 4-
37.20 7- 0.537 D 8- 0.102 8 5-1.71299
ν 5 San 53.8D 9- 0.397 N
S-1,84666v 6-23.9010-Variable Dll-0,136N 7-1.719Hν 7-50
．． 3DI2 San 0.295 N 8-1.805
18 ν 8-25.4013-variable 014-0.636 N 9-1.60311 ν
9-60.7DI5-0.113 016-0.227 017-0.397 N10-1.58913 Si1
0-61.2018-0.017 019-0.511 Nil abuse 1.58913
11m61.2020-0.255 R21--3,574 822-15,571 R23-2,559 R24--24,275 825-304,805 R2B-1,647 R27-4,933 R28--3, 808 R29-2,009 R30-34,483 R31-00 R:12- ω 02+- 0,170 0,017 0,715 1,232 Q, 102 0.147 0.295 0.017 0.363 Q, 568 0.681 N12-1.84666 N13-1.60311 N14 1.7495O N15-1.62299 N16-1.59551 N17-1.51633 ν12 23.9 13-60.7 v I4-35. 3 Shi15-58.1 ν 16-39.2 Shi17-64.1 Numerical Example 3 F-1~9.38 RI-14,793 R2-5,846 R3--15,311 R4-4, 891 85-10,825 86-16,380 n 7- 1.876 R8--2,246 R9-2,247 RIO~ -18,910 Old 1- -3.676 R12-4,372 RI3~ I3. 754 RI4- 7.323 1115- -3.863 RI6- Aperture R17-7,464 R18--13,38O R+9- 4.353 R20--12,945 FNo-1: 1.25 2 (&l-51, 3'
~5.9'~1.75 D I-0,284N I-1,80518ν l
I25.40 2-1.056 N 2-1.6
0311 ν 2-60.70 3- 0.022 D 4- 0.556 N 3-1.69680
v 3-55.505・Variable D 6-0.125 N 4-1.83400 ν
4-37.207-0.537 D 8-0.102 85-1.71299 ν 5~
53.80 9- 0.397 8 6 So 1.848
66 ν 6-23.9010-Variable Dll-0,13687-1,7+999 ν 7 books 50.30+2- 0.295 N B-1,8
0518ν B-25, 4D13-Variable D14- 0.636 8 9@1.603+1
ν 9-60.7015-0.113 DIB-0,227 017-0,397Nl0=1.51633 S1O
-84.1018-0.017 019-0.511 Ni1-1.5+633 Si1
1-64. ID20-0.221 R29- R2O- -3,528 22,597 2,520 -41,352 -42,765 1,634 4,958 -3,974 1,966 113,422 021 D25 So D27 Mar〇 30 glue 0.170 0.017 0.715 1.293 0.102 0.147 0.295 0.017 0.363 0.568 0.681 N12-1.84666 N13-1.60311 NI4 Sodium 1.7495Q N15-1.63854 N16-1.59551 NI7 1.5+633 12-23.9 ν 13-60.7 v 14=35.3 15-55.4 v 16-39.2 ν17-64.1 Numerical Example 4 F-1 to 9.38 RI-14,793 1 (2-5,846 83--15,311 R4-4,891 R5-10,825 R6@ 16.38O R7-1,876 R8 --2,246 89-2,247 10--18,91O R+--3,676 RI2- 4.372 R1:l-63,754 R]4・7.323 815- -:1.8B3 116- Aperture R17 12.108 RI8--13.818 8 9- 4.413 R20--12,161 FNo-1:1.25 2ω-51,3' ~5.9
゜~1.75 DI-0,284N Bow, 80518 ν 1
-25.40 2- 1.056 N 2-1.
60311 ν 2-60.7D 3- 0.02
2 D 4- 0.556 N D5/Variable D 6-0.125 D 7- 0.537 D 8-0.102 D 9-0.397 D〇-Variable DI-0,136 012-0,295 03・Variable 014-0.836 015-0.113 D 6-0.227 D17-0.340 N10-1.60311018
-0.017 DI9-0.511 N11-1.60311D20
-0.239 N 7-1.71999 ν N 5-1.71299 ν 3-1.69680 ν 3 Snow 55.5N 9-1
．． 60311 ν N 8 1.80518 ν N 6-1.84668 ν N 4-1.83400 ν 4 37.2 5-53.8 6-23.9 ? -50,3 8-25,4 9-60,7 Si10-60.7 υ11-60.7 R21--3,553 R22 Self 13.241 R23-2,558 R24-232,810 R25-747, 298 826-1,650 R27-4,693 828--3,310 R29 Maro 1.966 R30-8L184 R31 Tan ω R32-■ 023 Intimidation [129- [130- N12-1.84666 ν 12-23.90゜＋
70 0.017 0.625 813-1.69680 C13-55
．． 51.250 0.102 0.170 0.386 0.017 0.363 0.568 0.681 NI4-1.83400 Shi14-37.2NI7a
1.51633 v 17-64.1N16-1.5
6732 Shi16-42.8N15=1.60311
v15-60.7 (Table-1) (Effects of the Invention) As described above, according to the present invention, by setting the lens configuration of each lens group as described above in a 5-group zoom lens, it is possible to achieve a large F/1.2. A zoom lens with a high aperture ratio and a zoom ratio of around 10, with excellent aberration correction over the entire zoom range, low ghosting and flare, and high optical performance suitable for photo cameras and video cameras. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lens at the wide-angle end zoom position of Numerical Example 1 of the present invention, and FIGS. 2 to 5 are aberration diagrams of Numerical Examples 1 to 4 of the present invention, respectively. In the aberration diagram (
A) is an aberration diagram at the wide-angle end, (B) is an intermediate aberration diagram, and (C) is an aberration diagram at the telephoto end. In the figure, I, II, III, rV, and V are respectively 1st.
2nd゜3rd. 4th. In the fifth group, ΔM is a meridional image plane, ΔS is a sagittal image plane, d is a d-line, g is a g-line, and sp is an aperture. Engraving of the drawings (Fig.

Claims (1)

[Claims] (1) In order from the object side, the first group has a positive refractive power for focusing, the second group has a negative refractive power and has a variable magnification function, and corrects the image plane that changes due to variable magnification. It has five lens groups: a third group with negative refractive power, a fourth group with positive refractive power that allows the divergent light beam from the third group to exit in a divergent state, and a fifth group with an imaging function. The fifth group has two lens groups, a 51st group and a 52nd group, and the 1st group has a negative meniscus-shaped 11th lens with a convex surface facing the object side and both lens surfaces. convex first
The second lens group consists of a positive meniscus-shaped 13th lens with a convex surface facing the object side, and a negative meniscus-shaped 21st lens with a convex surface facing the object side.
The lens is composed of a laminated lens consisting of a negative 22nd lens whose both lens surfaces are concave and a positive 23rd lens, and the third group includes a negative 31st lens whose both lens surfaces are concave and a positive 3rd lens.
It consists of a laminated lens made by bonding two lenses together, and the fourth
The group consists of a positive 41st lens with both lens surfaces convex, and the 51st lens has a 511th lens with both lens surfaces convex, which also has a strong refractive surface facing the object side. Consists of four lenses: a 512th lens with both convex lens surfaces, a negative 513th lens with a concave strong refracting surface facing the object side, and a positive 514th lens with a convex strong refracting surface facing the object side. The 52nd lens group includes a negative 521st lens with a concave strong refractive surface facing the image plane side, and a 52nd lens with both lens surfaces convex.
The radius of curvature of the j-th lens surface of the i-th group is Ri, j, and the focal length of the i-th group is fi, The focal lengths of the 51st group and the 52nd group are f51, f52, respectively.
The refractive index and Abbe number of the material of the j-th lens in the i-th group are respectively Ni, j, νi, j, the center thickness or air gap of the j-th lens in the i-th group is Di, j, and the When the average refractive index of the materials of the 511th lens and the 512th lens is NA, 4.5<[(R5,1+R5,3)/(NA-1)]・
[1/f51]<7.0 0.125<[(N5,3-1)・f5]/[R5,6
]<0.250.55<[(R5,13)/(N5,7
-1)]・[1/f52]<0.6511<[(ν5,
6+ν5,7)/2]−ν5,5<150.3<D5,
A zoom lens that satisfies the following condition: 8/f5<0.4.