JPS63157118A - Zoom lens system - Google Patents

Abstract

PURPOSE:To obtain a miniature and high variable power lens system by providing an element whose radius of curvature can be varied, in front and in the rear of a diaphragm, and controlling an image surface position correction and a necessary variable power. CONSTITUTION:A zoom lens system is constituted by providing a first positive lens group F1 fixed in the course of zooming, a first negative lens group F2 for moving in the optical axis direction and executing a variable power extending from a wide angle end from an intermediate distance, an iris diaphragm F14, a positive lens group B1 of a relay part, a field diaphragm, an element V2 for varying a radius of curvature in front of the diaphragm R14 in addition of a second variable power system lens group B2, and an element V1 for varying a radius of curvature even in the group B2 in the rear of the iris diaphragm. In such a state, by the element V2 for satisfying an aplanatic condition, an image surface position at the time of a variable power which follows up a movement of the group F2 is corrected, and by the element V1 for satisfying a concentric condition, a variable power extending from an intermediate focal distance to a telephoto terminal in the group B1 is executed. By a constitution which is using this element which can vary a radius of curvature, a miniature and high variable power zoom system lens is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a zoom lens system, and in particular to a zoom lens system that applies an element whose radius of curvature can be changed, and which is compact and has a high zoom ratio used in televisions, videos, still videos, etc. The present invention relates to an imaging zoom lens system that provides the following.

[Prior art and its problems] There is a high demand for small size and high zoom ratio for imaging zoom lenses, and in order to satisfy this demand, the Japanese Patent Publication No. 61-760
No. 6 and Japanese Patent Publication No. 61-40965 have a built-in extension type. However, since these are switching magnification systems, a high degree of mechanical precision is required for securing lens storage space and aligning the optical axis, and furthermore, they cannot be used for continuous magnification change, so they have the disadvantage that they cannot be used except when changing shooting scenes, or It has the disadvantage that the F-number is as large as the telephoto end from the focal length position.

As another means, a zoom lens system is known, as seen in Japanese Patent Publication No. 52-4461, etc., which is provided with two zoom sections each consisting of four movable lens groups. However, in these systems, the second zoom section, which is installed on the image plane side, complicates the overall length of the lens due to the need to secure movement space and correct aberrations compared to a general relay part. It had some drawbacks.

[Means for Solving the Problems] An object of the present invention is to improve the above-mentioned problems and provide a compact zoom lens system with a high zoom ratio.

The above purpose is to provide a first variable magnification system that is installed in front of the aperture that determines the F-number of the system, and that moves the negative lens group in the optical axis direction to change the magnification within the intermediate focal ratio gI range from the wide-angle end. and a first diaphragm provided behind the diaphragm and whose radius of curvature can be changed.
a second variable magnification system comprising an element v1, which varies the magnification from an intermediate focal length to a telephoto end by the element Vl; and a second variable magnification system provided between the first variable magnification system and the second variable magnification system, A second element (2) whose radius can be changed is provided, and the element (v2) allows the above! This is achieved by a zoom lens system characterized by having the following: a variable power system of 81; and a correction system that corrects the image plane position accompanying the change in power of the second variable power system.

In other words, the present invention provides a variable power system that moves a negative lens group in the optical axis direction in front of the diaphragm, and a variable power system that uses the element Vl that changes the first radius of curvature in the rear, and furthermore provides a variable power system that uses the element Vl to change the first radius of curvature, and furthermore provides a variable power system that moves the negative lens group in the optical axis direction in front of the diaphragm. The above object is achieved by using a configuration in which the image plane position is corrected by the element v2 that changes the second radius of curvature.

Hereinafter, a zoom lens system according to the present invention will be explained in detail based on specific drawings.

FIG. 1 is a sectional view of a zoom lens system showing an embodiment of the present invention.

In this figure, Fl is the first positive lens group that is fixed during zooming, and F2 is the first negative lens group that moves in the optical axis direction and is responsible for changing the magnification from the wide-angle end to the intermediate focal length. This is the first variable power system. C is a correction system that includes an element v2 whose second radius of curvature can be changed and is in charge of correcting the image plane position when changing the magnification of F2 and correcting the image plane position when changing the magnification of B2, which will be described later. B1 is a positive lens group that is part of the relay.

B2 is a second variable magnification system that includes an element V] whose radius of curvature of fJSl can be changed, and that uses the element v1 to change the magnification from an intermediate focal length to a telephoto end.

The lens configuration of Fl and F2 is based on, for example, Japanese Patent Application Laid-Open No. 60-518.
This is the most common front lens system and variable power system disclosed in No. 13, etc., and in this example, a variable power ratio of 6 is obtained.

Further, C can also be used as a focusing system using the same method as previously filed Japanese Patent Application Laid-Open No. 61-80213, Japanese Patent Application Laid-Open No. 61-196216, and Japanese Patent Application Laid-Open No. 61-158213. At this time, as for the lens configuration, it is necessary to reduce the amount of occurrence and variation of spherical aberration and coma aberration, so the first surface of C is configured as a variable radius of curvature element v2, and the radius of curvature is within the range of change. It is desirable to satisfy the conditions of Aplanatic or Concentric.

That is, let the refractive index of 1 variable radius of curvature element 2 be n, the radius of curvature be RV2 (R23), and the object points of Fl and F2 be R.
When the length measured from the vertex of V2 is S (the object side from the surface vertex is negative and the image side is positive), the configuration is such that it satisfies either the following formula (2) or 0.

S= (n+l) RV2 −■S=R
V2 ...■Also, in order to shorten the overall length and aperture of the lens groups Bl and B2 behind the iris diaphragm, it is better to configure the lens group close to the object side with a positive lens group, and B2 has a plano-convex lens shape. The first surface of the lens is constituted by an element v1 having a variable radius of curvature, and a plano-concave lens made of optical glass is bonded to the rear of the element v1. Further, two positive lenses are added to the rear of this, so that even when the radius of curvature of vl is variable, the entire B2 forms a positive lens group. This second variable magnification system B2 changes magnification by changing the radius of curvature without moving the lens group in the optical axis direction. Compared to a configuration in which the magnification is changed by a movable lens group, no space between B1 and B2 is required for movement, so that the lens system can be avoided from becoming long and complicated. Furthermore, this configuration also allows for a fixed field stop (not shown in Figure 1) to be placed between the B1 and B2 lens groups, which eliminates unnecessary light from the periphery of the screen that causes aberrations on the telephoto side. It is also possible to take a blocking configuration.

However, in order to obtain a variable power ratio of 1.44 for this second variable power system,
The variable radius of curvature element vl must be changed from the intermediate focal length to the telephoto end in a direction that makes the focal length of B2 about twice as long. At this time, the power change amount of Vl is about 20
~30 dayopters are required, and the aberrations generated on this surface must be suppressed as much as possible.An effective measure for this is to use the method described above in C for the object point on the axis within the changing area of the radius of curvature of Ml. Similarly to the above, it is desirable to satisfy the concentric condition for the on-axis object point.

The above-mentioned a-formation of B2 also causes a change in the distance between the principal points of Bl and B2 at the same time when changing the radius of curvature of Vl, and this has the effect of promoting the variable power ratio of the second variable power system. Furthermore, it becomes an advantageous condition for correcting aberrations and downsizing the lens system.

Regarding the material for the variable surface shape elements Vl and V2 according to the present invention, silicone rubber is suitable from the viewpoint of transparency, homogeneity, mechanical properties, etc., so the refractive index of cl is n d =
1.408-1.509, 31 d = 52.
5 to 34.7. The molding method, driving method, etc. regarding the above-mentioned element are described in Japanese Patent Application Laid-open No. 60-84502, Japanese Patent Application Publication No. 60-111201, Japanese Patent Application Publication No. 60-114802,
JP-A-60-114804, JP-A-60-11480
No. 5, Japanese Unexamined Patent Publication No. 60-220301, etc. When the above-mentioned element is used, the center wall thickness generally changes, and the tendency is that the center wall thickness increases when a positive power change, that is, when a convex power is added to the surface shape, and the opposite phenomenon occurs when a negative power change occurs. Therefore, in consideration of this, in the embodiment, the center thickness of the variable surface shape element is slightly changed in the design.

Further, in the embodiment, only the curvature of one side of the element is changed, but both sides may be changed.

FIGS. 2(a), 2(b), and 2(c) are optical path diagrams of the first embodiment of the zoom lens system according to the present invention, respectively.

In the same figure, each focal length is f, (L) is when f=11.3, (b) is when f=67 (7), (C)
indicates the optical path when f=97.

[Effects of the Invention] As described above, according to the present invention, it is possible to achieve a compact zoom lens system for use in televisions, videos, still videos, etc., which can provide a particularly high zoom ratio.

[Example] Hereinafter, numerical examples of the present invention will be shown. In the numerical examples, Ri is the radius of curvature of the first lens surface in order from the object side, and Di is the thickness of the first lens and air in order from the object side. The distances Ni and νi are the refractive index and Abbe number of the glass material of the first lens, respectively, in order from the object side.

R30 in Numerical Example 1.2. R31 indicates the face plate, filter, etc. of an image pickup tube used in a bidet camera, etc.

ν −cIJC'l qt Kurotoφ−>>
＞ ＞ ＞＞ ＞＞N
22 2 2 2 2 2 Ill II II
1111 11110 -NC'l qp
C φ 2 22 2 χ 22 22 = Z II II II II II II I
Ⅱ II
I II II II II II II ll-1-cIJ
■Lie Kurotori φ0-~0 51, +,, -m m +1f
=Kousensen===Kousenkoku- II II II I
I 1111 II
II II ■ Low -
Moaning Loto>
＞ ＞ ＞ ＞＞
＞ ＞ ＞II
II II II 1
111 II II
II ■ O-I N ψ dimension
Pus Loto 2 2
Z Z 22 Z
Z ZII II II II
II II II II II II
II II II II II II
II II II II dimension NnCo ao ■ Low Nj dimension Kuroto ω ■ 0+l m II +T I-1+1
04～eIJ～～N～～～NKurororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororororo
I II ll II II II II II II
II groanncoto ψ■0-11N God's rotoro■〇--
-+1--m cIJ~C'JINetJ~N~Nv
0N-0 Sensenko R11 (oo) and R11 (Is) are the values when the object point is at infinity and 1 m from the first surface, respectively >>>>>>>>
>>'s −〜 Gin size pus rot ψ! Seagull -NM Liar Lotoω■0-Herororororororororororo〉〉〉〉〉〉〉
＞ ＞Ro omeIJ's groan ■ ト2 Z
Z 2 22 Z
Z Z+l m-m-++1-~NeJeJ
N～～～N～'s Rororororororororororororororo+1-1+l m-+l N eJ～N～～～NIN■Zeng-= Tadashi Sen - Sen = Ba wctggo:
= Country Sen -= Example 2. 58 ]0 ]0 ]0 U3 R11(co) and R11(1m) are the values when the object point is at infinity and 1m from the first surface, respectively.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a zoom lens system showing an embodiment of the present invention. FIGS. 2(a), 2(b), and 2(C) respectively show optical path diagrams of the first embodiment of the zoom lens system according to the present invention. Figure 3 (a), (b), and (c) are numerical example 1, respectively.
Figures 4 (a), (b), showing the longitudinal aberration of
(c) is a diagram showing the longitudinal aberration of Numerical Example 2, and in the diagram, ΔS and ΔM indicate the sagittal image plane and the meridional image plane, respectively. Agent Patent Attorney Johei Yamashita F 1.45 Spherical Ml difference Figure 3 (b) f=67 (, t/, 4.7 u=4.7゜-〇〇-

Claims (4)

[Claims] (1) The first lens, which is installed in front of the aperture, moves the negative lens group in the optical axis direction to change the magnification from the wide-angle end to the intermediate focal length range.
a second variable magnification system that is provided behind the aperture diaphragm and includes a first element V1 whose radius of curvature can be changed, and that uses the element V1 to vary the magnification from an intermediate focal length to a telephoto end; A second element V2 is provided between the first variable magnification system and the second variable magnification system and has a variable radius of curvature. A zoom lens system comprising: a correction system that performs image plane position correction as the magnification changes; (2) The zoom lens system according to claim 1, wherein focusing is performed by the second element V2 whose radius of curvature can be changed. (3) A patent claim characterized in that the second element V2 whose radius of curvature can be changed is configured to substantially satisfy an aplanatic condition with respect to an on-axis object point at a position within the changing region. A zoom lens system according to scope 1. (4) Claims characterized in that the first element V1 whose radius of curvature can be changed satisfies the condition of being substantially concentric with respect to an on-axis object point at a position within the changing region. The zoom lens system described in item 1.