JPH02118510A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain the zoom lens which is of F/1.6, has a variable power ratio as high as about 10 and is well corrected in aberrations over the entire variable power ratio by incorporating the lens system of 5-group lenses and constituting the lens so as to satisfy specific conditions. CONSTITUTION:The lens system is constituted, successively from the object side, of the 1st group I which has a positive refracting power for focusing, a 2nd group II which has a variable power function and a negative refracting power, a negative 3rd group III which corrects the image plane fluctuated by the variable power, a positive 4th group IV which emits the divergent luminous flux from the 3rd group III in a diverted state, and a 5th group V which has an imaging function. The lens system is so constituted as to satisfy the conditional equations I to V where the focal length at the wide angle end of the entire system is designated as fw; the radius of curvature of the i-th lens from the object side as Ri; the refractive index of the i-th lens as Ni, the average refractive index of the negative lens in the 2nd group as NIIN, and the average Abbe number of the lens in the 3rd group as nuIII.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zoom lens, particularly for photographic cameras and video cameras that have a high zoom ratio of about 10 and have good optical performance over the entire zoom range. The present invention relates to a compact zoom lens with a short overall lens length suitable for cameras and the like.

(Prior Art) Zoom lenses with a large diameter, high variable power, and high optical performance have been required for photographic cameras and video camera shades.

Among these, in zoom lenses for consumer video cameras, the number of pixels of image sensors such as CCDs has increased, and S-V II S'
With the improvement of recording methods 7, a high resolution of, for example, about 50 lines/mm in spatial frequency is required over the entire screen.

An example of a zoom lens with a variable power ratio of about 10 is λ, which is published in Japanese Patent Application Laid-Open No. 1973-
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 that has five lens groups: a fourth group for converting the light beam from the three groups into an afocal light beam, and a fifth group for imaging.

In general, in order to maintain high optical performance with a 5 JJ zoom lens while reducing the size of the entire lens system and increasing the zoom ratio, it is important to appropriately set the optical constants of each lens group that makes up the lens system. It becomes.

If you try to make the entire lens system more compact and have a high zoom ratio by increasing the refractive power of the valley lens group at +11, many higher-order aberrations will occur, such as spherical aberration at the center of the screen, coma aberration toward the periphery of both surfaces, and sasicle halo aberration. However, the aberration fluctuations during zooming also become larger, making it difficult to achieve high optical performance.
Ru.

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

As described above, photographing lenses used in video cameras are required to have good optical performance and not to generate harmful light such as ghosts or flares.

(Problems to be Solved by the Invention) The present invention solves the problem by appropriately setting the lens configuration of the quality lens group in the JT75 group zoom lens.
1, 6 culms, a zoom ratio of lO and a high tn ratio, and has high optical performance over the entire zoom range (in addition, when applied to a video camera etc., ghosts and flares due to light reflected from the image sensor surface are avoided). To provide a compact zoom lens that prevents the occurrence of.

(Means for solving problems) A first group with positive refractive power for focusing in order from the object side.

A second group with a negative refractive power that has a variable magnification function, and a third group with a negative refractive power that corrects the image plane that changes due to variable magnification.

It has five lens groups: a fourth group with positive refractive power that emits the diverging light flux from the third group in a diverging state, and a fifth group that has an imaging function, with the first group facing toward the object side. A bonded lens consisting of a negative meniscus-shaped first + lens with a convex surface and a twelfth lens with both lens surfaces convex; 5 a positive meniscus-shaped 13th lens with a convex surface facing the object; The second group consists of a negative meniscus-shaped 21st lens with a convex surface facing the object side, a negative 22nd lens whose both lens surfaces are concave, and a positive 23rd lens, which are bonded together. consists of a bonded lens in which both lens surfaces are concave and the negative 31st lens surface is convex, or a meniscus-shaped positive 32nd lens with the convex surface facing the object side is cemented, and the fourth group has both lens surfaces It consists of a 41st lens with a positive convex surface, and the focal length of the entire system at the wide-angle end is W, the radius of curvature of the first lens surface counting from the object side is Ri, and the refractive index of the material of the first lens is Ni.

The average refractive index of the material of the negative lens in the second group is N z ,
, when the average Abbe number of the lens material in the third group is i, 4.2 < RZ/rw < 4.
7・・・・・・・・・・・・(Eye 1.55<N*
(1,72・・・・・・・・・(2)1.7
4 < NXII (1,8L”・・・・・・
(3135kuν]ko [〈45・・・・・・・・・・・・
・+4+1, s'<N9(1,72...
- The following condition (5) must be satisfied.

(Example) FIGS. 1(A) and (13) are lens cross-sectional views at the wide-angle end and telephoto end zoom positions of Numerical Example 1 of the present invention.
In the figure, ■ is the first group with positive refractive power for focusing, 11 is the second group with negative refractive power for zooming, and m is on the object side to correct the image plane that changes with zooming. The third group has a negative refractive power and moves with a convex locus, and the fourth group has a positive refractive power and has a refractive power that allows the divergent light beam from the third group to exit in a diverging state.
3 is the fifth group that has a fixed imaging function, and SP is a fixed aperture.

In this embodiment, in such a zoom type, +i? As mentioned above, by specifying the lens configuration of each lens group from the first group to the fourth group and satisfying the first conditional expressions (1) to (5), aberration fluctuations associated with a high zoom ratio can be well corrected. High light over the entire magnification range? performance is obtained.

In particular, variations in various aberrations associated with high zoom ratios (1) For example, variations in longitudinal chromatic aberration and lateral chromatic aberration can be well corrected by appropriately setting the lens shapes of the second and third groups and the refractive index of the lens material. ing.

Additionally, 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 #3 is emitted in a diverging state, the reflected light flux from the sensor and filter is reflected by any lens surface, and the light flux from the image sensor This effectively prevents the occurrence of ghosts, flares, etc. due to re-incidence.

Next, the technical aspects of each of the above-mentioned conditional expressions will be explained.

Conditional expression (1) relates to the refractive power of the bonded lens surface in the first group, which is the second lens surface counted from the object side, and mainly relates to axial chromatic aberration.

This is a condition for suppressing changes in lateral chromatic aberration and spherical aberration due to zooming.

If the upper limit of conditional expression (1) is exceeded, the change in spherical aberration with respect to zooming becomes too large, and if the lower limit is exceeded, the change in axial chromatic aberration and lateral chromatic aberration with respect to zooming increases.

Conditional expression (2) relates to the refractive index of the material of the twelfth lens, which is the second lens from the object side, and is the upper limit of conditional expression (2), which is mainly a condition for correcting distortion in a well-balanced manner. If this value is exceeded, distortion at the wide-angle end increases, making it difficult to achieve good correction. Moreover, when the lower limit is exceeded, the halo at the telephoto end increases.

Conditional expression (3) relates to the average refractive index of the lens having negative refractive power in the second group, and is mainly a condition for reducing the Petzval sum and properly correcting spherical aberration. If the upper limit of is exceeded, the balance between the spherical aberration occurring in the second group and the spherical aberration occurring in the first group will be lost, and the spherical aberration at the telephoto end will worsen. Moreover, if the lower limit is exceeded, the Petzval sum increases in the negative direction, the curvature of the meridional image plane at the wide-angle end increases, and the change in chromatic aberration of magnification due to zooming increases, which is not good.

Conditional expression (4) concerns the average Abbe number of the material of the lens in the third group, which is a condition for good correction of axial chromatic aberration.If the upper limit of conditional expression (4) is exceeded, the telephoto end is reached. When the lower limit value is exceeded, the axial and chromatic aberrations at the wide-angle end increase and become difficult to correct.

Conditional expression (5) applies to the 4th group of the 9th a, in order from the object side.
Regarding the refractive index of the lens material, if the upper limit of the zero conditional expression (5), which mainly relates to the correction of spherical aberration, is exceeded, the Petzval sum increases in the negative direction, causing curvature of the meridional image plane at the wide-angle end. The burial mound is thick.

If the lower limit exceeds λ, the spherical aberration at the wide-angle end will increase, which is not good.

The zoom lens that is the object of the present invention is achieved by satisfying the above conditions, but in order to further shorten the overall lens length and achieve good aberration correction, the following conditions must be satisfied. It's better to let them.

The fifth group includes, in order from the object side, a 51st lens with both convex lens surfaces with a strong refractive surface facing the object side, a 52nd lens with a negative meniscus shape with a concave surface facing the object side, and a 52nd lens with a strong refractive surface facing the object side. a positive 53rd lens with its convex surface facing the object side, a negative meniscus-shaped 54th lens with its convex surface facing the object side, a positive 55th lens,
It has six lenses including a positive 56th lens with a strong refractive surface facing the object side, and the uniform refractive index of the material of the negative lens in the fifth group is Nvll. When the Petzval sum of a positive lens is pvp, 1.80<NVN
・・・・・・・・・・・・・・・・・・・・・・・・(6)
1.55<N+g<1.55・・・・・・・・・・・・
...(7) 0.055<I'VP<0. (+70・--
・−−・・・−・−・(&12.40 < l
1119 N Seal l <2.50...
...(9) 1, sO<lR24/fw|<1.6
The condition 0=.(101) is satisfied.

Conditional expression (6) concerns the average refractive index of the lens with negative refractive power in the fifth group.If the condition of conditional expression (6) is violated, the Petzval sum increases in the negative direction, resulting in a meridian image at the wide-angle end. This is not preferable because it increases the curvature of the surface.

Conditional expression (7) is related to the refractive index of the material of the 53rd lens, which is the third lens counted from the object side in the 5nth lens.If the upper limit of conditional expression (7) exceeds λ, the spherical aberration becomes negative at the wide-angle end. If the lower limit value is exceeded, coma aberration increases at the wide-angle end, which is not good.

Conditional expression (8) relates to the Petzval sum of the lens having positive refractive power in the fifth group, and is mainly a condition for setting a good balance between the wide-angle end and the telephoto end of the curvature of the meridian image plane.

Conditional expression (9) concerns the refraction and refracting power of the negative lens surface of the 52nd lens with its concave surface facing the object side.
It is mainly used to correct spherical aberration and astigmatism in a well-balanced manner regarding the refractive power of the negative lens surface with the concave surface facing the image surface side of the lens.

When the upper limits of conditional expressions (9) and (lO) are exceeded, spherical aberration increases on the telephoto side, and when the lower limits of conditional expressions (9) and (10) are exceeded, astigmatism increases on the wide-angle side. It's not good because it will come.

Incidentally, in the above description, the refractive power of a strong refractive surface on the object side is compared to the refractive power of the other surface, that is, the lens surface on the image surface side.

Next, numerical examples of the present invention will be shown.
i is the radius of curvature of the 4th lens surface from the object side, D
i is the first lens thickness and air gap from the object side, Ni
and νi are the refractive index and Abbe number of the glass of the ia-th lens, respectively, in order from the object side. Furthermore, n29. +130 is the glass block of the face plate of the 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 Examples F-1 to 9.40 R1-11,53 R2-4,39 R3 Snow -11,29 R4 Tomi 3.59 R5-7,89 R6-11,01 87-1,34 H8--1 ,53 R9-1,69 RIG--9,51 R11--2,73 RI2 depth 3.23 R13 depth 53.14 RI4- 9.02 115- -2.42 RIG-diaphragm RI7- 3.85 2ω- 15,83@ ~51.04" FNO-1:1.65~2.4 D I-0,213 02-0,792 03-0,017 D 4- 0.417 N 3-1.696800
5. Variable D61I0.093 07- 0.418 08- 0.076 09- 0.298 DIG 婁 Variable 011 Proverbs 0.102 012- 0.221 013- Variable 014- 0.451 015 Proverbs o, ass 016- 0 .17 017- 0.417 M S-1,71299 N l-1,805+8 ν 1-25.4N
7 Proverbs 1.71999 N 6.1.84666 N 2-1.60311 ν 2-60.7N
4-1.8340O N 8-1.8051δ N 9-1.60311 N10-1.62299 ν 3 Sodium 55.5 ν 4-37.2 ν 5-53.8 ν 6-23.9 ν 7 Snow 50 .3 ν B-25,4 ν 9-60.7 S10-58.1 RI8- -6.30 )+19- -2.41 R20--32,06 R21-, 2,62 R22--9, 21 823--30,64 R24-1,52 RZ5- 4.04 R26 Snow -3,07 R27-1,46 R28 Seal -29,77 1 (29 Lightning 00 R30-ω 1318- 0.206 019- 0 .127 1320- 0.012 021- 0.477 022m 1.725 023- 0.102 024- 0.0'u 025- 0.238 026- 0.012 027- 0.332 028- 0.426 029- 0.511 N11-1.84666 N12-1.60311 N13-1.11340O N14-1.51823 NIS-1,54072 N16 1.51633 ν11 23.9 ν12-60.7 13-37.2 ν14 -59.0 ν15-47.2 ν16-64.1 Numerical Example 2 FIII~9.311 FNOJ: 1.6s~
2.40 2ωm5.83' ~5
1.04 ”R1-13,101ro l-0,213
N 1111.80sI8 v Ill 2
5.41+2s4.336 02nd 0.784 N
2-1.638s4 v21Iss, 4R3--1
3,52503-0,017R4-3,782R411
G, 417 N3111.1i9680
y3 seal 55.5R5-9,95905-variable R6-5,74706 0.093 N4
-1.83400 y437.2R7-1,2
9107-0,432 R81I -1,523[18-0,076N5l1
1.7+999 y51160.3R9-1,
632f)! -0,298N6-I44666 Sig-23.9RIG-710.020 010- Variable RIII -2,486DI+= 0.10
2 N? -1,69680v 7 proverbs N5.
5RI21I4.744 DI2aO, 213Ng-
1,80s18 SI1llI25.4RI3-17
2.780 013- Variable R14-10,5220
14-0,451N9m1.69680y9-5
5.5R15--2,790015-0,085RII
S-Aperture 1) 016@0.17R1? -4,083
017-0,401FIIOll, 6+1311
ylo-60,7Rlg--6,049 R19--2,467 R2O--49,533 821-2, Fu07 R22--9,176 R23--61,434 R24-1,528 825-3,700 R26--3,484 R27-1,502 R2g--27,576 R29-lXl R30-G.

l8I1 0+9- 〇2B- 0,211 0,119 0,0+2 0,485 1,593 0.102 0.111 0.255 0.012 0°315 0,426 0.5■ N11-1.14666 N12- Supervisor, 63854 N13-1.8340O NI4-1.5+823 NI5-1.53172 N16-1.51633 ν11-23.9 ν12-55.4 ν13 Proverbs 37.2 ν14-59.0 ν! 5 婁 48゜9 ν16-64.1 Numerical example 3 Fsl~9.3JI FNOiIl: 1.6s
〜2.40 2ωTomiS, 83' 〜
51.04 "RI-12, 2730l Proverbs 0.21
3 N +-1,80s18 ν l-
25,4R21I4.415-02w0.792
N 2 1.56384 v 2-60.71+
3- -10.770 D 3- 0.017R4
-3,64904-0,434N3-1.69680
ν 3-55.5R5 snow 9.674!
35- Variable R6-6, 16606-0,093N
4-1.80610 ν 4-40.9R7-1,
33911710,432 +18- -1.590 08- 0.076 N
5-1.696110 ν s. 55, 51 (9
-1,72409-0,298N6-1.64666
v 6- 23.98IO@-35,419
010-Variable R11--2,663Dll-0,102N7-1.7
1999 ν 7-50.3RI21+3.913
012- 0.221 N11.80578
ν B-25,4RI3-208.119 013-
Variable R14-8,741014-0,451N9 snow 1.63854 ν 9-55.4815-
-2.627 015- 0.085+116- Aperture 016- 0.17R17-4,030017-
0,417Nl0-1.62299 ν10-5
8.1 old 8's ~5.871 old 9- -2.422 R20,-110,8116 R21-2,610 R22I+-9,02g I (23 irises -42,1+54 R24-1,542 R2S-3, 097 1126--3, +49 R27I11.463 R2B-13,253 829IICO R3G' o.

r) 18- zo- 024 proverb 027 # 2g- 0.20g 0.127 0.0+2 0.477 Summer, 667 0.103 0, 092 0.238 0゜012 0, 332 0, 426 0.511 NI+- 1,84666 N12 Snow 1.60311 N13-1.801i1G N14-1.51823 NIS, 1.54072 NI6-1.511+33 νI+-23,9 ν! 2-60.7 13-40.9 14-59.0 5-47.2 ν16-64.1 (Effect of 9 brightness) According to the present invention, the 5-group zoom lens is By setting the lens configuration of each lens group as described in 1, F/1.8. To achieve a zoom lens suitable for photographic cameras and video cameras that has high optical performance, has a high zoom ratio of about 10, performs aberration correction well over the entire zoom range, has few ghosts and flares, and has high optical performance. I can do it.

[Brief explanation of the drawing]

Figures 1 (8) and (13) are cross-sectional views of the lens at the wide-angle end and zoom position of the numerical example 1 of the present invention, and Figures 2 to 4 are numerical examples 1 to 1 of the present invention, respectively. FIG. 3 is a diagram showing various aberrations of No. 3. In the aberration diagram, (A> is the aberration diagram at the wide-angle end, (B) is the aberration diagram at the middle, and (C) is the aberration diagram at the telephoto end. 3
, fourth and fifth groups, ΔM is the meridional image plane. ΔS is the sagittal image plane, d is dlQ, gLtglA, SP
is the aperture. (Table-1) (A) Figure (A) Figure (B) Figure (C) Figure (C) Figure (A) Figure (Δ) Figure (B) Figure (C) Non- Point aberration laa length (9) Lateral chromatic aberration

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 a negative refractive power, a fourth group with a 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 first group is a bonded lens consisting of a negative meniscus-shaped 11th lens with a convex surface facing the object side and a 12th lens with both lens surfaces convex, and a positive meniscus-shaped lens with a convex surface facing the object side. The second group consists of a negative meniscus-shaped 21st lens with a convex surface facing the object side;
The third group consists of a bonded 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 negative 31st lens whose both lens surfaces are concave or A meniscus-shaped positive third with a convex surface facing the object side.
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 being convex, the focal length of the entire system at the wide-angle end is fw, the radius of curvature of the i-th lens surface counting from the object side is Ri, and the radius of curvature of the i-th lens is When the refractive index of the material is Ni, the average refractive index of the material of the negative lens in the second group is @N_II_N@, and the average Abbe number of the material of the lens in the third group is @ν_III@, 4.2< It is characterized by satisfying the following conditions: R2/fw<4.7 1.55<N_■<1.72 1.74<@N_II_N@<1.83 35<ν_III<45 1.55<N9<1.72 A zoom lens. (2) The fifth group includes, in order from the object side, a 51st lens with convex surfaces on both surfaces with a strong refractive surface facing the object side, a 52nd lens with a negative meniscus shape with a concave surface facing the object steel, and a 52nd lens with a negative meniscus shape facing the object side. A positive 53rd lens with a strong refractive surface facing, a negative meniscus 54th lens with a convex surface facing the object steel, a positive 55th lens, and a positive 56th lens with a strong refractive surface facing the object side. It has six lenses, and when the average refractive index of the material of the negative lens in the fifth group is @N_V_N@, and the Petzval sum of the positive lens in the fifth group is P_v_p, 1.
80<@N_V_N@ 1.55<N_1_2<1.65 0.055<P_v_p<0.070 2.40<|R19/fw|<2.50 1.50<|R24/fw|<1.60 The zoom lens according to claim 1, wherein the zoom lens satisfies the following conditions.