JPH0350516A - Compact high-power zoom lens system - Google Patents

Abstract

PURPOSE:To compensate aberrations excellently while the power is high by moving a 1st and a 4th lens group in one body to the object side along the optical axis and moving a 3rd lens group which is a small-power convex lens having its concave surface on the object side along the optical axis. CONSTITUTION:The 3rd lens group 3 uses the small-power convex lens which has the concave surface on the object side and is moved along the optical axis so as to correct image plane variation and the 1st lens group 1 and 4th lens group 4 are moved in one body to the object side along the optical axis. For zooming from the wide-angle end(W) to the telephoto end(T), the 1st lens group 1, a 2nd lens group 2, and the 4th lens group 4 are moved monotoneously to the object side and the 3rd lens group 3 is moved to the image side temporarily so as to compensate the image plane variation and then moved to the object side. A gap D1 of lens groups increases and a gap D2 increases temporarily and then decreases. A gap D3 decreases or decreases and then increases. Consequently, the compact zoom lens system of high power which has aberrations compensated excellently is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-magnification zoom lens system with a simple structure used in compact cameras and the like.

[Prior Art] In recent years, there has been a demand for the use of zoom lens systems to be able to capture images ranging from wide-angle to telephoto, even in highly portable compact cameras, etc. In response to this demand, various zoom lens systems for compact cameras have been being developed. Two-group or three-group zoom lens systems have been developed to simplify the structure, but they are not only difficult to obtain high magnification, but also suffer from various aberrations during zooming. The drawback was that correction was difficult. Therefore, as the demand for more sophisticated compact cameras increases, 4-group zoom lens systems have come to be widely adopted. However, although a 4-group zoom lens system has the advantage of being able to correct aberrations well and obtain high magnification, it has a complicated structure and is bulky, so the original advantages of a compact camera are lost. There was a point of no return.

(Means for Solving the Problems) In view of the current situation, the present invention provides positive first
It consists of a lens group, a positive second lens group, a positive third lens group, and a negative fourth lens group, and moves the first lens group, second lens group, and fourth lens group toward the object side along the optical axis. In a zoom lens system that continuously changes the focal length from wide-angle to telephoto by moving the lens, the third lens group is a low-power convex lens with a concave surface facing the object, and the optical axis is adjusted to correct image plane fluctuations. This is a compact high-power zoom lens system characterized in that the first lens group and the fourth lens group are moved together along the optical axis toward the object side. [Operation] In the present invention, during zooming, the positive first lens group, the positive second lens group, and the negative fourth lens group are monotonically moved toward the object side, and the positive third lens group is moved toward the image plane. By moving along the optical axis to compensate for fluctuations, the focal length can be changed continuously from wide-angle to telephoto, and the third lens group is a convex lens with low power with a concave surface facing the object side. , the first lens group and the fourth lens group can be moved by the same amount by zooming, and the structure can be simplified.

In FIG. 1 showing a movement diagram of the zoom lens system according to the present invention, 1 is a first lens group with a positive composite focal length;
is the second lens group with a positive composite focal length, 3 is the third lens group with a positive composite focal length, 4 is the fourth lens group with a negative composite focal length, X is the optical axis, and P' is the imaging position It is.

The first lens group 1 is a lens group for correcting spherical aberration, especially on the telephoto side, and includes at least one positive lens and at least one negative lens.

The second lens group 2 is a lens group that corrects aberration fluctuations due to focusing, especially curvature of field aberration, and is
It consists of at least one positive lens and at least one negative lens in the front and at least one positive lens and at least one negative lens in the rear.

The third lens group 3 is a lens group that corrects variations in field curvature due to zooming, and is composed of at least one positive lens. The fourth lens group 4 consists of at least one positive lens and at least one negative lens. In FIG. 1, when zooming from the wide-angle end (W) to the telephoto end ('r), the first lens group l, the second lens group 2, and the fourth lens group 4
is moved monotonically toward the object, and the third lens group 3 is first moved toward the image side so as to correct the image plane fluctuation, and then moved toward the object side, or the third lens group 3 is moved toward the object side. Move monotonically. At this time, the first lens group l and the fourth lens group 4 are moved integrally by the same amount of movement. This devastation can be done in a straight line or in other ways. Therefore, the structure of the 41I zoom lens system can be simplified. During zooming from the wide-angle end (W) to the telephoto end (T), the distance DI between the first lens group l and the second lens group 2 increases, and the distance between the second lens group 2 and the third lens group 3 increases. The distance D2 between them increases once and then decreases. The distance D between the third lens group 3 and the fourth lens group 4 decreases or decreases and then increases.

At this time, focusing may be performed by either the first lens group l1, the second lens group 2, or the fourth lens group 4. In the present invention, it is desirable that the following conditions be satisfied.

(+) 0<fw/f3<O. l 5 This conditional expression is for correcting field curvature aberration etc. that occurs during zooming, where f1 is the focal length of the entire system at the wide-angle end (W), and [3 is the third lens group 3 is the focal length of If the lower limit of this conditional expression is not satisfied, it will be difficult to correct curvature of field aberration at an intermediate focal length, and if the upper limit of the above conditional expression is not satisfied, it will be difficult to correct spherical aberration at an intermediate focal length. ．． [Example] Hereinafter, numerical examples of the present invention having the basic lens configuration shown in FIG. 2 will be shown.

The lens structure shown in FIG. 2 is as follows.

The first lens group 1 consists of a cemented lens L, +I, 2 consisting of a negative meniscus lens L with a convex surface facing the object side, a positive meniscus lens L2 with a convex surface facing the object side, and a cemented lens L, +I, 2 with the convex surface facing the object side. Positive meniscus lens L. It consists of The second lens group 2 includes a biconcave negative lens L4 and a biconvex positive lens L.
, and a biconcave negative lens L. cemented lens with t. sl. & and a negative menis cemented lens L9+L with the convex surface facing the object side.
．． . It consists of The third lens group 3 consists of a positive meniscus lens Ll+ with a concave surface facing the object side. The fourth lens group 4 is a positive meniscus lens L with a concave surface facing the object side.
12, and biconcave negative lenses L and C. The lens L7 of the second lens group 2 and the lens L. A diaphragm S is arranged between the two.

In the description of the numerical examples below, m: surface number rI counted sequentially from the object side = radius of curvature of the first lens surface counted from the object side dl: radius of curvature of the first lens surface counted from the object side Thickness or air spacing nI: Refractive index for the d-line of the first lens component counting from the object {jl νI: Atsube number f' of the first lens component counting from the object side: Synthetic focal length of the entire system [ 3f': Back focus.

The specific configuration of the first embodiment is shown in the table below.

m r d
n ν1 88.673 1.80
1.7B472 25.72 42.10
5 3.4B [51633 64.13
125.990 0.20 4 29.983 5.01! ．． 5163
3 64.15 543.390 Variable 6 -92.850 1.00 1.516
33 64.17 12.531 0.5
9 8 20.534 5.00 1.6476
9 33.99 -10.929 1.00
1.74400 44.910 645.
160 0.3527.397 16.155 265.450 26.667 169.120 18.484 -17.85"7 1B.975 lL692 27.070 +7.957 17.637 115.610 f' 39.20 60. 00 +11.40 d, 3.76 11.08 1.88 5.76 4,54 0.50 1.00 5.23 Variable 2.00 Variable 4.2o l.96 1.60 Bf' 9.04 23 .47 56.40 dl? l.56 5.60 1.59551 1.51633 1.78472 1.62230 1.51633 1.18412 1.74300 17.35 5.99 39.2 64.1 25.7 53 .l 64.l 25.7 49.2 T 19.56 1.56 1.55
The aberration curve with this specific configuration is shown in Figure 3. Next, the specific configuration of the second embodiment is as shown in the table below.

m r d n ν1
100.81 1.80 1.805172
5.52 41.81 3.23 1
．． 5B913 61.23 100.39
0.20 4 32.02 4.57 1.62
299 5B. 15 317.94 Variable 6-122.87 1.00 1.516
33 64.17 12.676 0.5
6 8 20.217 4.98 1.64
769 33.99 -11.017 1
．． 00 1.74400 44.910 1
05B. 90 0.3611 27.8B3
2. Q5 1.59551 39.212
15.4'75 5.9113 2B5.0
3 4.85 1.52633 64
．． 114-26.549 0.50 15 185.860 1.00 1.
78472 25.716 18.586
5.22 1.62230 53.11
7 -17.861 Variable 1B-18.982 2.00 1.51
633 64.119 -18.643 Variable 20-28.445 4.20 1.80
518 25.521-18.426 1
．． 8922-18. OV0 1.60 1
．． 77250 49.623 115.999 f'Of' Angle of view fi1 39.20 9.04 59
'N 60.00 23.51 39
”T 111.40 56.62 22
'ds dtt d+qW 3
．． 84 1.56 1'7.23N
11.12 5.14 6.37?
19.51 1.56 1.56 The aberration curve with this specific configuration is as shown in Figure 4. A third aberration curve diagram of each of the first and second embodiments.
, 4 shows that each aberration is sufficient for practical use. [Effects of the Invention] As is clear from the above explanation, according to the present invention, the first
A convex lens with low power that has a concave surface facing the object side by making the lens group or the fourth lens group a convex-convex-concave structure and moving the first and fourth lens groups together along the optical axis toward the object side. By moving the third lens group along the optical axis to correct image fluctuations, it has become possible to provide a compact zoom lens system with high magnification and well corrected aberrations.

[Brief explanation of drawings]

FIG. 1 is a diagram of movement B of the zoom lens system in the present invention.
Figure 2 is a layout diagram of each lens when each lens group of the basic lens configuration of the present invention is set to wide-angle and telephoto.
Aberration curve diagram of the embodiment, FIG. 4 is an aberration curve diagram of the second embodiment. L1...L13: 1st lens to 13th lens X:
Optical axis S: Aperture radius of curvature of each lens surface Thickness of each lens or air gap

Claims (1)

[Claims] In order from the object side, a positive first lens group, a positive second lens group,
Consisting of a positive third lens group and a negative fourth lens group, the focal length can be changed from wide-angle to telephoto by moving the first, second, and fourth lens groups toward the object side along the optical axis. In a zoom lens system that continuously changes the field of view, the third lens group is a convex lens with low power with a concave surface facing the object side, and is moved along the optical axis to correct image plane fluctuations. A compact high-power zoom lens system characterized in that the fourth lens group and the fourth lens group are moved integrally toward the object side along the optical axis.