JPH03228007A - Zoom lens - Google Patents

Abstract

PURPOSE:To easily make the power variation high while reducing the size of a lens system on the whole by employing lens constitution where a 1st, a 2nd, and a 3rd group are put in partial discharge of power varying operation. CONSTITUTION:This zoom lens is equipped with four lens groups, i.e. a 1st group I with positive refracting power, a 2nd group II with negative refracting power, a 3rd group III with positive refracting power, and a 4th group IV in order from the object side, and when the power is varied from the wide-angle end to the telephoto end, the 1st group and 3rd group are moved to the object side so that the air gap between the 1st and 2nd groups increases, the air gap between the 2nd and 3rd groups decreases and the air gap between the 3rd and 4th groups increases. Consequently, the small-sized zoom lens has a 62 deg. view angle of photography, an about 3.7 power variation ratio, and high optical performance over the entire power variation range of the high power variation ratio while shortened in overall length.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zoom lens, and in particular, a zoom lens with a wide angle of view of about 62 degrees at the wide-angle end, a variable A8 ratio of 3.7 degrees, and a high zoom ratio. The present invention relates to a compact zoom lens suitable for photographic cameras (still cameras), video cameras, etc., which has high optical performance over the entire zoom ratio range.

(Prior Art) Zoom lenses for recent still cameras, video cameras, etc. are required to have a wide angle of view and a high f-power. Generally, when trying to widen the angle of view of a zoom lens, many high-order aberrations occur, and it becomes difficult to properly correct them. In addition, in order to achieve a high zoom ratio, it is necessary to strengthen the refractive power of each lens group and increase the amount of lens movement.
Generally, along with this, the diameter of the front lens increases, the overall length of the lens also increases, and the entire lens system becomes larger.

The present applicant previously disclosed in Japanese Unexamined Patent Publication No. 61-69016 that the angle of view at the wide-angle end is about 62 degrees, the zoom ratio is about 3.7, and the lens has a relatively short overall length with a high zoom ratio. We are proposing a compact zoom lens.

The zoom lens disclosed in this publication consists of four groups, in order from the object side: the first group with positive refractive power, the second nth group with negative refractive power, the third group with positive refractive power, and the fourth group with positive or negative refractive power. It has two lens groups,
When changing the magnification from the wide-angle end to the telephoto end, the first group and the third group
The groups are integrally moved toward the object side, and the second group is moved to the first group. By moving the lens non-linearly with respect to the movement of the third group, and thereby having the second and third groups share the variable power function, it is possible to shorten the overall length of the lens and achieve high variable power.

(Problems to be Solved by the Invention) The present invention utilizes the refractive power arrangement of the zoom lens proposed in Japanese Patent Application Laid-Open No. 61-69016, which the applicant previously proposed, and further improves the lens configuration of each lens group. In particular, the overall length of the lens has been shortened, and the angle of view at the wide-angle end is approximately 62mm, and the zoom ratio is 3.
．． The purpose of the present invention is to provide a zoom lens having a wide angle of view of about 7.7 mm and high optical performance over the entire zoom range with a high zoom ratio.

(Means for Solving the Problems) The zoom lens of the present invention includes, in order from the object side, a first group with positive refractive power, a second group with negative refractive power, a third group with positive refractive power, and a third group with positive refractive power. It has four lens groups, and when changing power from the wide-angle end to the telephoto end, the air distance between the first and second groups increases, and the air distance between the second and third groups decreases. , move the first group and the third group toward the object side so that the air gap between the third group and the fourth group increases, set the focal length of the first group to fi, and set the focal length of the entire system at the telephoto end. When the distance is fT and the imaging magnification at the telephoto end of the second group for an object at infinity is β2T, then 0, 85< β2T <-0,65...
...(1) 0.45<fl/fT<0.65
......(2) 0.1 <|f2/fT|< 0.15...
・(3) 0.12< f3/fT < 0.3...
...(4) It is characterized by satisfying the following conditions.

(Example) Fig. 1 is an explanatory diagram showing the paraxial refractive power arrangement of the zoom lens of the present invention, and Figs. 2 to 4 are numerical example 1 of the present invention to be described later.
3 is a cross-sectional view of the lens at the wide-angle end.

In the figure, ■ is the first group with positive refractive power, II is the second group with negative refractive power, ■ is the third group with positive refractive power, and ■ is the fourth group with positive or negative refractive power. . The arrows indicate the locus of movement of each lens group during zooming from the wide-angle end to the telephoto end.

In this example, each lens group is configured to satisfy each of the above-mentioned conditional expressions, and when changing the magnification from the wide-angle end to the telephoto end, the air gap between the first group and the second group increases, and the distance between the second group and the second group increases. The first group and the third group are moved toward the object flPI so that the air distance between the third group and the third group decreases, and the air distance between the third group and the fourth group increases. Further, the second group is moved to the J+- curve as necessary. In this embodiment, the first to third groups are moved at different speeds as the magnification is changed.

In this example, when changing from the wide-angle end to the telephoto end (at step 6, the first
By moving the group toward the object side and increasing the air distance between the second group and the second group, the second group can change the magnification of the first group;)
In order to promote the 0 river and shorten the total lens length at the wide-angle end, -'1:': + variable aj (the ratio is set to 8. Also, the third lens group is similarly moved to the object 0-1. Along with the 2nd group, the 3rd edition also shares the 8th effect.

In this embodiment, the first, second, . 1 each in the 3rd group
By adopting a structure that shares eight negative rivers,
This makes it easy to achieve high variable power while reducing the size of the entire lens system.

Next, the technical meaning of the above-mentioned Tanijo I'1 formula will be explained.

Conditional expression (1) is for appropriately setting the imaging magnification range at the telephoto end of the second group, thereby making it possible to miniaturize the entire lens system and to perform focusing by the second group.

When the limit value of conditional expression (]) is exceeded, the specified magnification ratio is obtained.
) to wide-angle (II imaging magnification must be reduced,
Along with this, it is necessary to increase the refractive power, which increases the occurrence of various aberrations. If the lower limit of formula (1) is exceeded, the slope of the lens driving cam will become steeper, and the same magnification (-1)
Exceeding this is not a good idea because focusing will only be possible with the second group.

Conditional expression (2) relates to the refractive power of the first group.1. This is to reduce aberration fluctuations accompanying zooming, and to effectively impart a predetermined zooming action to the second group ζ.

If the upper limit of conditional expression (2) is exceeded, the movement of the first group during zooming must be increased, and as a result, the lens diameter of the first group increases. Furthermore, at the wide-angle end, the distance between the second and third groups must be increased by p, which increases the overall length of the lens. If the lower limit of equation (2) is exceeded, the aberration variation due to zooming will increase, and the sensitivity, which is the ratio of the image plane variation to the deviation in the optical axis direction of the first edition, will increase, and the manufacturing grain size will increase. It's not good because it can become difficult.

Conditional expression (3) relates to the refractive power of the second group and is mainly intended to maintain good optical performance while reducing the size of the entire lens system.

If the upper limit of conditional expression (3) is exceeded, the magnification effect of the second lens group will decrease).
When the amount of movement of the group must be increased, the total length of the lens, which must be secured in advance in the lens system in a predetermined movement space, increases.

If the lower limit of conditional expression (3) is exceeded, spherical aberration on the telephoto side will be over-corrected, and coma and astigmatism 'φ' will increase with zooming.
iE increases the movement and compensates for these various aberrations in a well-balanced manner.
It becomes difficult to do so.

Conditional expression (4) relates to the refractive power of the third group, and is mainly intended to satisfactorily correct various aberrations while ensuring a predetermined variable power ratio.

If the upper limit of conditional expression (4) is exceeded, the hack focus becomes longer than necessary, and the total length of the lens increases. If the lower limit of conditional expression (4) is exceeded, aberration fluctuations due to zooming will increase, making it difficult to satisfactorily correct spherical aberration, especially on the telephoto side.

In addition, in this example, the refractive power of the 4nth lens is relatively weak due to the lens configuration, so even if it is moved during zooming, the effect of zooming will be small. Therefore, it is difficult to decide whether to keep it fixed during zooming or to decide whether the lens barrel is simple. It's good because it becomes

Also, it is preferable to configure the fourth group with negative refractive power because the lens system as a whole can have a stronger teletype tendency, and the overall length of the lens can be easily shortened.

The zoom lens that is the object of the present invention can be achieved by satisfying the above conditions.Furthermore, it is possible to reduce the size of the entire lens system while satisfactorily correcting aberration fluctuations associated with zooming, and to cover the entire zooming range. In order to obtain high optical performance, each lens group is preferably configured as follows.

In order from the object side, the first group includes a meniscus-shaped negative eleventh group.
It has a cemented lens with a twelfth lens having a convex lens surface, and a meniscus-shaped positive thirteenth lens, and the second group includes a meniscus-shaped negative second lens with a convex surface facing the object side.
1 lens, a 22nd lens with both lens surfaces concave with a strong refractive surface facing the object side, and a 2nd lens with both lens surfaces convex.
3 lenses, and a meniscus-shaped negative 24th lens with a convex surface facing the image side, and the third group includes two positive TS3 lenses with a strong refractive surface facing the object side, and a 32nd lens,
A positive 33rd lens with a strong refractive surface facing the object side, a negative 34th lens with a strong refractive surface facing the image side, and a positive 35th lens with both lenses and both lens surfaces convex, Said fourth
The group is composed of a negative 41st lens with a strong refractive surface facing the object side and a positive 42nd lens with a strong refractive surface facing the image plane side.

Note that a refractive surface that is strong on the object side means compared to the image surface side. The same applies to a refractive surface that is strong on the image plane side.

In the zoom lens according to this embodiment, large spherical aberrations and axial chromatic aberrations occur from the first group due to zooming.

For this reason, the first lens group is constructed as described above, and the lens thickness is made as thin as possible to satisfactorily correct these various aberrations. In particular, the first lens and the twelfth lens are cemented to reduce the occurrence of axial chromatic aberration, and the spherical aberration produced by the cemented lens and both lens surfaces is used to correct the spherical aberration produced by the entire first group. The refractive power of the first group is shared by the positive thirteenth lens, and the curvature of each lens surface is weakened to correct various aberrations in a well-balanced manner.

Distortion aberration is mainly corrected favorably by the 21st lens in the lens configuration of the second group. Positive spherical aberration occurring at each diverging lens surface of the 22nd lens is corrected by increasing the refractive power of the object-side converging lens surface of the 23rd lens. The higher-order aberrations that occur when the positive refractive power of the object-side lens surface of this 23rd lens is increased are replaced by spherical aberrations, which are difficult to generate even if the negative refractive power is increased. This is corrected by the object-side lens surface of the 22nd lens, both of which have strong concave lens surfaces.

Furthermore, the air lens formed by the 23rd lens and the 24th lens corrects various aberrations that occur due to the aberration in a well-balanced manner. Note that it is preferable for aberration correction to configure the air lens at this time to have a convex shape toward the image plane side.

In this example, when the radius of curvature of the object side lens surface of the 22nd lens and the lens surface of the image plane fll are respectively R8 and R9, and the radius of curvature of the object side lens surface of the 23rd lens is RIO, lR101<1R81<lR91. This is preferable for correcting aberrations.

Further, the refractive index of the material of the 21st lens and the 22nd lens is set to N4. If N5, then 1.7<N4 1.7<N5 It is possible to use a material with a high refractive index to increase the radius of curvature of the lens surface, to reduce the occurrence of higher-order aberrations, and to reduce distortion. good.

Furthermore, if it is possible to correct the chromatic aberration that occurs in the second group, 1, 8<N4 1, 8<N5 It is better to

The third group has a relatively strong positive refractive power, and in this embodiment, the light beam incident on the third group is a strongly divergent light beam.

For this reason, three positive lenses of a predetermined shape are arranged on the object side of the third group, and by sequentially converging the diverging light beam with the three positive lenses, the outer diameter of the lens can be made smaller while generating higher-order aberrations. is decreasing. Furthermore, the 34th lens is a negative lens, and the front principal point of the third group is displaced toward the object side, thereby shortening the overall length of the lens.

In particular, the refractive power of the lens surface on the image side of the 34th lens is made into a strong concave surface to cancel out various aberrations occurring in the 3rd group.
Various aberrations occurring in the third group as a whole are corrected in a well-balanced manner. Further, in this embodiment, the 35th lens is constructed of a biconvex lens with both lens surfaces being convex, that is, the lens surface closest to the image plane of the third group is a convergent lens surface, so that various aberrations are well corrected. There is.

As mentioned above, the fourth group is composed of two lenses, and mainly corrects chromatic aberration and off-axis aberration in a well-balanced manner. In particular, fluctuations in astigmatism due to zooming are effectively corrected.

That is, in this embodiment, the aperture is integrated with the third group or
It is placed close to the group and moved as the magnification changes. As a result, the incident position of the off-axis light beam passing through the 4nth lens changes as a result of the change in angle A8, thereby satisfactorily correcting astigmatism.

In addition, in this embodiment, the third lens of the third lens group is
It is preferable to make at least one lens surface of the five lenses aspherical in order to eliminate the absolute 1a of spherical aberration and the zoom variation component, and to reduce the zoom variation component of coma aberration and the absolute (J') of astigmatism.

In addition, in this embodiment, a so-called flare diaphragm that moves on the optical axis for variable magnification is provided between the third and fourth groups to effectively eliminate flare that occurs in the middle of the angle of view. This is preferable because it allows you to do many things.

Next, numerical examples of the present invention will be shown. In numerical examples R
i is the curvature T-diameter of the first lens surface from the object side 1, Di is the thickness and air gap of the first lens from the object side, and Ni and νi are the curvature T-diameter of the first lens surface from the object side, respectively. This is the refractive index of crow and the number.

The aspherical shape has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis,
The traveling direction of the light is positive, R is the paraxial radius of curvature, A, B, C,
It is expressed by the formula when D is each an aspherical coefficient.

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

Numerical Example I F-36,:] ~+31 R1・+91.67 R2-58,88 R3-177,75 R4-37,51 R5-101,06 R6-77,15 87-14,70 R8-- 41,39 R9-54,44 RIo・ 2805 R11--46,42 R12--22,56 R13-103,61 8I4~ (2 F) RI5- 28.24 RJ5-325. [10 R17-21,64 R18・102.65 R1! ! -31,71 FNo-1:4 2ω-61,6゜7
~5.6 ~18.7°D 1・
2.40 N +-1,80518ν l-25
,402-7,00N 2-1.60311 ν
2-60.7D 3-0.12 D 4-4.40 N 3・1.60311
ν 3-60.7D5・Variable D 6-1.25 N 4-1.77250 ν 4
-49.6D7・5.15 D 8-1.00 N 5-1.80400 ν 5
-46.609-0.50 DIo・4.00 86-1.80518 ν 6-2
5.4DI+-1,10 Di2-1.00 N 7-1.77250 ν 7
-49.6D13・Variable 014- 1.00 015- : 1.60 88-1.55962 v
8-6], 2D15-0.15 D]7・3.30 N 9-1.51633 ν 9
-64.1D18-0.40 D19・5.31 N10-1.51633 Shi10
-64.1R20-58,70 R21-2154,79 822-14,72 R23-19,40 824--62,00 (Aspherical) R25/Flare diaphragm R26--23,73 R27-624,35 R28- -20,14 020-0,80 021-2,00 D22- 1.25 023- 4.00 024-Variable D25-Variable D26- 1.10 027- 4.6G 1l-1 4686 N12・1.64759 N13 -1.7859O N1 1.53256 11-23.9 b12 33.8 13-44 ν 14-45 Aspheric coefficient - 8-2,29113xlO-' C-1,08793xlO-8 Numerical example 2 F-: I6.3 ~131.7 RI-193,70 82-58,99 R3・-171,07 R4・3728 R5-97,60 86・79.10 87 injection 14.76 R8--41, 70 R9-54,82 RIO-28,08 R11--46,74 R12--22,61 R13--10510 RI4・ (Aperture) R]5- 28.33 818・-303,83 817-22,38 R18-96,75 819-30,66 FNo.! :4 2ω・61.6'～5.6
~18.7゜D I-2,40N
1・1.80518 ν l−25,4D 2−
7.00 N 2-1.50311 ν
2-60.7D 3・012 D 4・4.40N 3□1.80311
v 3-50.7D5・Variable D 6-1.25 N 4・1.77250 ν 4
-49.6D7・5.15 D 8-1.00 N 5-1.80400 ν 5
・46.6D 9-0.50 010-4.00 86・1.805+8 ν 6-2
5.4Dll-1,10 DI2・1.00 N 7-1.77250 ν 7
-49.6013・Variable DI4-1.00 015-3.60 N 8・1.55962 ν 8
-61.2DI6・0.15 017-3.30 N 9-1.51633 ν 9
~64.1DI8-0.40 019-5.1i0 N10・1.51633 Si1
0-64.1R20-60,62 R21-1329,38 R22-14,81 R23-19,48 R24--62,00 (Aspherical) R25-Flare diaphragm R26 -2342 827-584,18 R28-- 19,84 020-0,80 D21- 2.00 022- 1.25 D23- 4.00 024-Variable D251-Variable D26- 1.10 D27- 4.6O N11-1.84666 N12-1.64769 N13 -1.7859O N14-1.53256 11-23.9 12-33.8 13-44.2 14-45.9 Aspheric coefficient 8- B-2,2554X 1O-5 C-1 ,04924xlO-' Numerical Example 3 F-36,3 ~131.7 RI-181,13 R2-55,94 R3-123,08 R4-35,44 R5-90,34 R6-93,40 87-15 ,47 88--45,15 89 line 50.14 8IO-28,1O R11--48,93 R12--21,73 R13--89,13 814-(aperture) R15-43,04 RI6-513. 92 R17-27,27 RI8- 56.17 R19-23,49 FNo-1: 4 ~ 5.6 2ω-61,6° ~ 13.7' 01・ 2.30 0 2- 7.50 D 3- 0.12 0 4- 4.50 D5-Variable D 6- 1.25 D 7- 4.90 D 8- 1.00 09-0.50 DIO-3,90 Dll-1,10 012-1,00 013-variable 014- 1.50 015 2.85 016-0.15 017- 2.80 D18-0.25 D19-9.00 1-1.80518 2-1.55962! -25,4 2-61,2 3-1.55962 3-61.2 4-1.77250 4-49.6 5-1.80400 5-46.6 6 Akebono 1.80518 6-25.4 N 7-1.77250 ν 7■49.68-1
．． 60311 8-60.7 9-1.58913 9-61.2 N10-1.51633 10-64.1 R20-316,74 R21-: ]16.74 822- 14.96 R23-19,38 R24 -72,50 (Aspherical surface) R25-7 Rare aperture R26 volume -26,15 R27-171,30 R28--21,53 D20~0.00 021- 3.60 D22- 1.25 023- 3. 50 024・Variable D25-Variable 026- 1.20 027- 5.6O N11-1.84666 N12-1.64769 N13-1.8061O N14-1.53256 Sill-23,9 Sill-12-33.8 Sill 13-40.9 14-45.9 Aspherical coefficient A OB-190481xlO-'C--6,69143xlO-" (Table 1) (Effect of the invention) According to the present invention, 4 of a predetermined refractive power By setting the movement conditions for zooming of the two lens groups and the lens configuration of each lens group as described above, it is possible to shorten the overall lens length while achieving a shooting angle of view of 62 degrees, a zoom ratio of 3, and a wide TPj degree. It is possible to achieve a compact zoom lens that has high optical performance over the entire zoom range with a wide angle of view and a high zoom ratio.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the paraxial refractive power arrangement of the zoom lens of the present invention, FIGS. 2 to 4 are lens sectional views at the wide-angle end of numerical examples 1 to 3 of the present invention, and FIGS. 5 to 7 are FIG. 3 is a diagram showing various aberrations of numerical examples 1 to 3 of the present invention. In the y-diagram (A)
shows the wide-angle end, (B) shows the middle, and (C) shows the telephoto end. In the figure, ■ is the first group, n is the second group, ■ is the third group, and ■ is the fourth group.
group, SP is a diaphragm, FP is a flare diaphragm, ΔS is a sagittal image plane, and 6M is a meridional image plane. Figure 831E/ ■ ■ ■ Work V 1 ■ ■ ■ Figure (A) Distortion aberration with sine condition # points on spherical convergence (4) Figure (C) Stop L equation 1 (Back figure (8) Ta3 7 figure (A) 51 pages 1+ required figure (C)

Claims (1)

[Claims] (1) Four lens groups: a first group with positive refractive power, a second group with negative refractive power, a third group with positive refractive power, and a fourth group in order from the object side. When zooming from the wide-angle end to the telephoto end, the air distance between the first and second groups increases, the air distance between the second and third groups decreases, and the air distance between the third and fourth groups increases. moving the first group and the third group toward the object so that the air distance between the first group and the third group increases;
When the focal length of the i-th group is fi, the focal length at the telephoto end of the entire system is fT, and the imaging magnification at the telephoto end of the second group for an object at infinity is β2T, -0.85<β2T<-0 A zoom lens that satisfies the following conditions: .65 0.45<f1/fT<0.65 0.1<|f2/fT|<0.15 0.12<f3/fT<0.3. (2) The zoom lens according to claim 1, wherein the fourth group is fixed during zooming. (3) The zoom lens according to claim 1, wherein the fourth group has negative refractive power. (4) In order from the object side, the first group includes a cemented lens made of a meniscus-shaped negative eleventh lens and a twelfth lens whose both lens surfaces are convex, and a meniscus-shaped positive thirteenth lens, Said second
The group consists of a meniscus-shaped negative 21st lens with a convex surface facing the object side, a 22nd lens with both concave lens surfaces with a strong refractive surface facing the object side, a 23rd lens with both convex lens surfaces, and an image plane. It has a meniscus-shaped negative 24th lens with a convex surface facing the side, and the third group has a 24th lens with a strong refractive surface facing the object side.
a positive 31st lens and a 32nd lens, a positive 33rd lens with a strong refracting surface facing the object side, a negative 34th lens with a strong refracting surface facing the image side, and a positive lens with both lens surfaces convex. Third
5 lenses, and the fourth group includes a negative 41st lens with a strong refractive surface facing the object side and a positive 42nd lens with a strong refractive surface facing the image plane side. Claim 1
Zoom lens listed. (5) The zoom lens according to claim 4, wherein at least one lens surface of the 35th lens is an aspherical surface. (6) The zoom lens according to claim 4, further comprising a flare removal diaphragm that moves during zooming and is arranged between the third group and the fourth group.