JPS6256917A - Small-sized zoom lens - Google Patents

Abstract

PURPOSE:To obtain a small-sized zoom lens which has high optical performance by providing two lens groups and making one lens surface of the 1st or 2nd lens group and the object-side lens surface of the 6th lens aspherical. CONSTITUTION:The 1st lens group which has positive refracting power and the 2nd group which has negative refracting power are provided successively from the object side and the gap between both lens groups is varied to perform power variation. At least one lens surface of the 1st lens group is made aspherical so that the refracting power is larger at a position of 100% in lens surface effective diameter than at a position of 90%. In another way, at least one lens surface of the 2nd lens group is made aspherical so that the negative refracting power is smaller at a position of 90% in lens surface effective diameter than at a position of 100%. Further, the object-side lens surface of the 6th lens is made aspherical so that the negative refracting power is smaller at the lens peripheral part than at the center part. Thus, the optical performance of the small-sized zoom lens is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a compact zoom lens, and in particular to a lens shutter camera, a video camera, etc., the effective pack focus is short and the entire length of the lens (from the first lens surface to This invention relates to a small zoom lens with a short distance m> to the image plane.

(Prior Art) Recently, with the miniaturization of lens shutter cameras, video cameras, etc., there has been a demand for compact zoom lenses with short overall lens lengths. Particularly in the field of small cameras such as zoom shutter cameras that do not require lens replacement, it is desired to attach a zoom lens. There is a demand for a small zoom lens with a length comparable to that of conventional single focus lenses.

Many zoom lenses, including the standard angle of view commonly used in lens-shutter cameras (photographing angle of view of 2ω-47 degrees, focal length of about 50111+1 when converted to a still camera), have been proposed in many ways, including Japanese Patent Publication No. 49-29146. has been done. This basic zoom lens consists of two lens groups, the 1st lens group with negative refractive power and the 1@2 lens group with positive refractive power, in order from the object side, and the magnification is varied by changing the distance between both lens groups. However, because the refractive power is arranged in order from the object side to negative and positive, the puck focus is relatively long, which is a desirable configuration for a single-lens reflex camera, but the overall lens length tends to be too long for a lens shutter camera. Ta.

The present applicant previously disclosed in Japanese Unexamined Patent Application Publication No. 57-201213 that the system is composed of two lens groups, a first lens group having a positive refractive power and a second lens group having a negative refractive power, in order from the object side. We proposed a compact zoom lens that changes the magnification by changing the distance between the two.

In this publication, since a positive and negative refractive power arrangement is adopted in order from the object side, a zoom lens 1c with a relatively short pack focus and a short overall lens length is achieved.

(Problems to be Solved by the Invention) The present invention further improves the compact zoom lens that the present applicant previously proposed in Japanese Patent Application Laid-Open No. 57-201213, has a brighter F-number, and has variable magnification. The purpose of the present invention is to provide a compact zoom lens that has a zoom ratio of about 2 times and has good optical character performance over the entire screen.

(Means for solving the problem) There are two lens groups on the object side and the body: a first lens group with positive refractive power and a second lens group with negative refractive power, and the distance between both lens groups is In a compact zoom lens that performs magnification by changing the lens, the first lens group includes a meniscus-shaped lens with positive refractive power with a convex surface facing the object, a second lens with concave surfaces on both sides, and a second lens with concave surfaces on both sides. Cure the third lens whose lens surface is convex and the fourth lens (4-) whose lens surfaces are both convex,
The second lens group has two lenses: a meniscus-shaped fifth lens with a positive refractive power having a convex surface facing the image plane side, and a sixth lens having a negative refractive power with a concave surface facing the object side; The direction of at least one lens during the first run is set to 9 of the effective diameter of the lens surface.
It is composed of an aspherical surface having a shape in which the positive refractive power is stronger at the 100% position than at the 100% position, or at least one lens surface in the z-th lens is compared to the position at 90% of the effective diameter of the lens surface. The negative refractive power is weaker at the 100% position, and the lens surface on the object side of the sixth lens is configured so that the negative refractive power at the periphery of the lens is greater than the negative refractive power at the center. It is composed of form Ei 7 which also makes it weak.
``°4 shout'' 1. The features of this invention are described in the implementation column.

(Implementation row) FIG. 2 is a cross-sectional view of the lens of the number 1 direct implementation [HJ 1] of the present invention. In the same figure, (4) is a wide angle! , (B) shows the zoom position in telephoto mode.

In the figure, l is the first lens group with positive refractive power, ■ is the second lens group with negative refractive power, and both lens groups are moved toward the object side while decreasing the distance between them. The magnification is changed. With such a refractive power arrangement, this embodiment achieves a zoom lens with a short pack focus and a minimum overall lens length at the wide-angle end.

In addition, in this implementation row, each lens configuration of the first lens group and the second lens group, and at least one of the @l lens or the second lens
By applying aspherical surfaces having the above-mentioned shape to the two lens surfaces and the object-side lens surface of the sixth lens, aberration fluctuations due to aberrations are reduced and various aberrations of the entire screen are well corrected.
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In particular, the halo from the center to the middle of the screen on the telephoto side is well corrected.

FIG. 1 is an explanatory diagram of the effect when one lens surface of the first lens group is made an aspherical surface.

In the figure, Gl, G2, and G3 are the second and third lenses of the shoulder 11, respectively. The lens directions R1, R2, R3, and R4 of the first and second lenses are all spherical surfaces on the gold plate, and the light is incident at an incident height hA, and the spherical convergence d of the nine-axis rays is well corrected. In this case, 1i4iI and 9aB, which are incident at a more striped incidence height hB than the upper source JA, pass through the eleventh second lens as shown by the broken line in the figure.

On the other hand, if the spherical aberration is not sufficiently corrected after the third lens G3, the ray B will have overcorrected spherical aberration due to the influence of many local astigmatisms and other aberrations. to conclude.

For this reason, in this practical array, if we surround it, is the first lens an aspherical surface? When applying an aspherical surface to the second lens, the aspherical shape should be such that the periphery of the lens effective surface has a stronger positive refractive power than 90% of the lens effective surface, and when applying an aspherical surface to the second lens, However, the lens is configured such that the negative refractive power at the periphery of the lens effective surface is weaker than at 90% of the lens effective surface.

As a result, the optical path indicated by the broken line in the same figure is corrected to become a four-point optical path, and spherical aberration, especially spherical aberration at the telephoto end and low, are corrected well. Diameter ratio t
-It's true.

Generally, when correcting spherical UM aberration, it is effective to introduce an aspheric surface into the lens surface where the height of incidence of the axial light beam on the lens surface is high.

Therefore, as long as there are four lenses in the IF lens group, an aspherical surface may be applied to any lens surface, but in this embodiment f! In A1, in particular, the lens surface of the first or second lens is made aspherical. As a result, the height of incidence of the extraneous light beam on the aspherical surface is made as high as possible, and off-axis low aberrations are also well corrected at the same time.

In addition, by making the object-side lens surface of the sixth lens an aspherical surface shaped so that the negative refractive power is weaker at the periphery than at the center, the image surface characteristics at the intermediate portion of magnification increase in the negative direction. This also prevents distortion on the wide-angle side from increasing in the positive direction.

In the present invention, it is preferable to perform focusing by extending the entire lens system to reduce aberration fluctuations, but it is also possible to perform focusing by moving only the first lens group or the second lens group. According to this, the lens barrel becomes simple.

Next, numerical implementation sequences of the present invention are shown. R in the numerical implementation sequence
i is the radius of curvature of the first lens surface from the object side, D
I is the first lens thickness and air distance from the object side, N1
and ν are the refractive index and Abbe number of the glass of the first lens, respectively, in order from the object side.

The aspherical shape has the X axis in the optical axis direction, the KY axis in the direction perpendicular to the optical axis, the direction of light propagation as positive, the intersection of the vertex of the lens and the X axis as the origin, and R as the paraxial radius of curvature of the lens surface. , a-tech + 6
2 + 13, *a * 15.

b engineering, b2. b3. When b4 is an aspherical coefficient, + a4Y8+ a5Y” + bIY3+ b2Y5
+b3Y'+b4Y9.

Also, [0-03JC) display is 110-3Jt' meaning-i
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Numerical implementation sequence I F-3&06~71.19 FNO-1:19~5.
12ω-59, 2”-33, number R1-17, 93D
l-3,09N l field 1.53113
ν 1-6L 4rL 2- 81.22 02-
1.84R3--19,65D 3-1.93
N 2-1.7B590 ν 2-4 Table 2R
4-25,9204 Rumor 0.39 R5-35,4405-4,65N5-L51633
C3-641R6--17.62 D 6-0
．． 22R7-59, 56D 7-L 1(i N
4-1.51633 4-6411ζ8--2
5.66 08-variable R9= -25,9309-
3,417N 5-1.69680 v 5-b
5-5RIO--16,32DIO-4,53・R11
--14,55Dll-1,62N 6-1.61J
311 ν 6-60.7Rt2--2tti
, 16 It l; Aspheric coefficient a --Z646D-06R3--7,3U9D-08
R4-7,177D-10a5=-1,1720-12
R11 surface; aspherical surface a = -9,1600-03az-'L115D-05
a a= 47380-07 & 4--
Z571D -09=s=-6,2810-12 I) Torture-&609D-O5b2-Ippan 1920-06b
3--1.395L)-L18 b4-Z929D
-10R1 surface; curvature of 100% effective diameter half trowel 18.47
Radius of curvature of 90% effective diameter L & 53 Number ILII! Implementation row 2 F-3&02~71.11 FNO-1:3.8-5
2ω-59,3°~318°ltl”17.87
Dl=Z14 Nl”1.53113 yl
-62h4R2-76, 1802-139 R3--19,62D 3402 N 2-1.78
590 Shi2-44.2R← 2FL87 D
←α43 R5-34, 25L) 5-470 N3-1.51
6J3 C3-64. IR6--17.47
0-to 22 R7-61, 36L12-121 N 4-1.
51633 ν 4-64.1R8--25,8
608-Variable kL 9--25.71 L)') & d5
N5-1. (i41680v
5”55.5RIO--1ti, 41 DIG
-Table 54all--14 (io D11=1.6
2 N 6-1.60311 v 6-6a
? lζ12-225.14 Rj; Aspheric coefficient a2-6.645D-06a3-Z5 (30-08-t
, 4”-7,4950-10a5” 1933D-12
R+1; Aspherical coefficient al--9,003D-03a2-10290-05&
3D 4.742D-0714 layer-2,392D-09
a5--6.1880-12 bl--6,211D-05bl--5,4130-0
6b3--L198D-08b, -λ893D-10R
2; Effective diameter IO portion surface curvature radius 6295 Effective diameter 90% radius of curvature 6a, 77 Numeric value M column 3 F-3427 ~ 64L54 FNO-1: Fu8 ~ 52
ω-645~35″R1-16°64 D 142
6 N l-1,60311ν l-6 (17R>
77.19 D 2-1.63R3--20,
03D 3-172 N 2-1.80610
C2-40.9R4 3λ22 D 4-α
44R5= 66, 97 05-IL 84
N 3-1.60311 C3=-60.7R6
--17.58 D 6-0.15R7-122
,62D 7-1.87 N 4-1.60311
Shi4-60.7R8--35,2608-variable R9--21,43D 9-3.04 N 5"1
．． 71700 ν5=47.9RIO--15,3
0DIO-4, 11R11--14, 81Dll-1,
fiON G-1, 60311 Jiro 60.7R12-
-91,51 R3; Aspherical coefficient m s -1,1799D-12 R11; Aspherical coefficient a --9,8430-03a --7,2350-0
6a-1,1350-07a-:1.5211)-
093〆Todoro m s -16650-12 b l ・-'2. ．． 697 D-05b 2, -Z
6 (IGI) -06b3--2.8650-0
8 b4--1.086D-1083 plane; effective diameter 1
Radius of curvature at 0% part -20,16 Radius of curvature at 90% effective diameter -20,09 (Effects of the present invention) As described above, according to the present invention, the entire screen has an F number of about 5 and a variable magnification ratio of about 2. It is possible to achieve a compact zoom lens with a short overall lens length of about 12 (lens overall length/no-point distance at the wide-angle end) and which achieves excellent aberration correction over time.

Simple explanation of the table drawings - Fig. 1 is an explanatory diagram of the effect of the aspherical surface according to the present invention, Fig. 2 is a cross-sectional view of the lens of the numerical implementation row 1 of the present invention, Figs.
The figures are various aberration diagrams of the a series 1 to 3 of the present invention, 1 in the figure.
．． ff are the first and second lens groups, respectively, (B),
<(5 is various aberration diagrams at wide-angle end, intermediate, and telephoto zoom positions, S and C are sine conditions, g is g-line, d is daI, △
S indicates a sagittal image plane, and 6M indicates a meridional image plane.

Claims (1)

[Claims] A small zoom lens that has two lens groups, a first lens group with positive refractive power and a second lens group with negative refractive power, in order from the object side, and performs magnification by changing the distance between both lens groups.
The first lens group includes a meniscus-shaped first lens with a positive refractive power with a convex surface facing the object side, a second lens with both concave lens surfaces, a third lens with both lens surfaces convex, and a third lens with both lens surfaces convex. The second lens group includes a meniscus-shaped fifth lens with a positive refractive power with a convex surface facing the image side, and a negative refractive power with a concave surface facing the object side. a sixth lens, and the positive refractive power of at least one lens surface in the first lens is stronger at a position of 100% of the effective diameter of the lens surface than at a position of 90% of the effective diameter of the lens surface. or at least one lens surface in the second lens is composed of an aspherical surface having a shape in which the negative refractive power is weaker at a position of 100% of the effective diameter of the lens surface than at a position of 90%. , a compact zoom lens characterized in that the object-side lens surface of the sixth lens is formed of an aspherical surface having a shape such that the negative refractive power at the peripheral part of the lens is weaker than the negative refractive power at the center part. .