JPH0643613U - Zoom lens device for small camera - Google Patents

Abstract

(57) [Abstract] [Purpose] A zoom lens device for a camera, which is composed of a 4 type optical lens, corrects aberrations, enhances the quality of photographs, reduces cost and downsizes the camera. [Structure] A first lens system, which is a condenser lens, and a second lens system, which is a divergence lens system, and the first lens system is composed of two lenses, a concave lens on the object space side and a convex lens on the image space side. , The second lens system is composed of two crescent moon lenses which are divergent lenses, and the optical surface of the first lens of the second lens system is convex toward the object space. When the zoom lens zooms from the wide-angle end to the telephoto end, both lens systems are simultaneously moved in the object direction, and at the same time, the distance between both lens systems is shortened as the focal length becomes longer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a zoom lens device used for a small camera, and more particularly to a zoom lens device capable of correcting aberrations with a minimum optical lens system, improving the quality of photographs, reducing costs and downsizing the camera.

[0002]

[Prior art]

 In the conventional zoom lens technology for cameras, camera zoom lens devices having a zoom ratio of 1.3 to 2.0 are classified into the following two types.

(A) The structure of the zoom lens device of the first type of camera comprises a first lens system which is a diverging lens system and a second lens which is a condenser lens system. The first type of camera zoom lens has a drawback in that it has a very long back focal length and cannot cope with downsizing of the camera. Moreover, the aperture of the first lens system is relatively large, and at present, it is only used for a single-lens reflex camera.

(B) The zoom lens device of the second type of camera is an improvement of the drawbacks of the zoom lens device of the first type of camera, and the zoom lens device of the second type camera has Is a telephoto lens in which the first lens system is a condensing lens system and the second lens system is a diverging lens system, and the rear focal length is shorter than that of the zoom lens device of the first type camera. The zoom lens device of the second type of camera is used in most twin-lens reflex cameras.

[0005]

[Problems to be solved by the device]

 Regarding the construction of the above-mentioned second type lens system in the prior art, the one described in US Pat. No. 4,682,680 is typical of the prior art, but at least five or more optical lenses are used. In addition to being complicated in structure, it was also expensive to manufacture.

[0006]

[Means for Solving the Problems]

 The zoom lens device for a camera according to the present invention is a zoom lens device for a small camera, which includes four optical lenses. From the side of the object space in which the object exists, the four optical lenses are divided into two lens systems, a first lens system and a second lens system, and the first lens system is a condenser lens system and a second lens system. Is a diverging lens. When the zoom lens device of the camera performs zooming movement from the wide-angle end to the telephoto end, both lens systems simultaneously move in the object direction, and at the same time, the distance between both systems becomes shorter as the focal length becomes longer.

The first lens system having a condensing characteristic in the embodiment of the present invention is composed of two lenses, a concave lens on the object space side and a convex lens on the image space side, and a second lens system having a divergence characteristic is It consists of two crescent lenses, which are divergent lenses. The optical surface of the first lens of the second lens system is convex toward the object space. The first lens system and the second lens system each have at least one aspherical surface. With the above lens system configuration, it is possible to reduce the number of lenses and obtain a good quality photograph.

[0008]

[Action]

 The zoom lens device of the camera of the present invention corrects aberrations by a lens system including a minimum number of optical lenses, can take high-quality pictures, and can reduce the size and cost of the camera.

[0009]

【Example】

 Examples will be described with reference to the drawings. The present invention relates to a zoom lens device for a small camera, and more particularly to a zoom lens device for a camera used for a 35 mm type camera.

FIG. 1 is a configuration diagram of each lens of a zoom lens device of a camera of the present invention. The zoom lens device of the camera of the present invention is an optical lens system including four lenses (1), (2), (3) and (4). This lens system is composed of a first lens system F including lenses (1) and (2) and a second lens system R including lenses (3) and (4) from the subject side. The first lens system F is a condenser lens system and the second lens system R is a divergent lens system. A space SP is formed between the first lens system and the second lens system, and when the lens system performs zooming movement from the wide-angle end to the telephoto end, the first lens system F and the second lens system R simultaneously move to the left. The distance between the two groups, that is, the space distance SP, becomes shorter as the focal distance becomes longer.

In the embodiment of the present invention, the first lens system F is a condenser lens system and is composed of a lens (1) and a lens (2), and the lens (1) on the object space side is a lens surface on the object space side. Is a concave lens whose radius of curvature is smaller than 0, and lens (2) is a convex lens. The lenses (3) and (4) constituting the second lens system R are concave lenses which are divergent lenses, and the optical surface of the lens (3) is convex toward the object space.

In each symbol shown in FIG. 1, S1 and S2 are the lens surface of the lens (1), S3 and S4 are the lens surface of the lens (2), S5 and S6 are the lens surface of the lens (3), and S7 is , S8 are the lens surfaces of the lens (4). I is the image plane. Further, each lens system of the first lens system F and the second lens system R has at least one aspherical surface.

In the zoom lens device of the camera of the present invention, the movement of the first and second lens systems in the object space direction is remarkable, and at the same time, the spatial distance between both lens systems is changed to achieve the zoom objective. To do. Also, the zoom lens device of the camera of the present invention is composed of only four optical lenses, which can reduce the manufacturing cost.

FIG. 1 shows the configuration of the basic lens system of the zoom lens device of the camera. Two embodiments will be specifically described in the present invention. The first embodiment is shown in FIGS. 2, 3 and 4, and the second embodiment is shown in FIGS. 7 The values for both examples are shown in the table below, respectively.

[0015]

[First embodiment]

[0016]

[Table 1]

Among them, the aspherical surface characteristic is expressed by the following polynomial.

[0018]

[Equation 1]

Materials for the aspherical surface of the first embodiment are as follows.

[0020]

[Table 2]

Next, materials of the second embodiment of the present invention will be shown, and the reference numerals in the table are the same as those in the first embodiment.

[0022]

[Table 3]

Materials for the aspherical surface of the second embodiment are as follows.

[0024]

[Table 4]

[0025]

[Effect of device]

 INDUSTRIAL APPLICABILITY The zoom lens device of the present invention can be used in a camera to improve the quality of photographs, reduce the manufacturing cost, and reduce the size of the camera.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a lens system of a zoom lens device of the present invention.

FIG. 2 is a side view of the first embodiment of the present invention at the wide-angle end.

FIG. 3 is a side view of the first embodiment of the present invention at an intermediate focal length.

FIG. 4 is a side view of the first embodiment of the present invention at the telephoto end.

FIG. 5 is a side view of the second embodiment of the present invention at the wide-angle end.

FIG. 6 is a side view of the second embodiment of the present invention at an intermediate focal length.

FIG. 7 is a side view of the second embodiment of the present invention at the telephoto end.

FIG. 8 is a side view of the third embodiment of the present invention at the wide-angle end.

FIG. 9 is a side view of the third embodiment of the present invention at the intermediate focal length.

FIG. 10 is a side view of the third embodiment of the present invention at the telephoto end.

[Explanation of symbols]

(1), (2), (3), (4) lens S1, S2 lens surface of lens (1) S3, S4 lens surface of lens (2) S5, S6 lens surface of lens (3) S7, S8 lens (4) Lens surface F First lens system R Second lens system SP Space

Claims (4)

[Scope of utility model registration request] 1. A zoom lens device for a camera comprising a front first lens system and a rear second lens system, wherein the front lens system is a condenser lens system and the second lens system is a diverging lens system. And a space is formed between the first lens system and the second lens system, and when the zoom lens of the camera performs zooming movement from the wide-angle end to the telephoto end, the first lens system and the second lens system are provided at the same time. It is moved in the spatial direction, the distance between both lens systems is shortened as the focal length becomes longer, and the first lens system is composed of two lenses, a concave lens on the object space side and a convex lens on the image space side, and a second lens system. A zoom lens device for a small camera, characterized in that it is composed of two concave lenses. 2. The zoom lens device for a small camera according to claim 1, wherein the lens on the object space side of the second lens system is a crescent lens which is a diverging lens convexly directed to the object space side. 3. The zoom lens device for a small camera according to claim 1, wherein the lens on the image space side of the second lens system is a crescent lens which is a diverging lens convexly convex to the image space side. 4. -0.38 <R1 / fw <-0.2,
Satisfies the condition of 0.4 <f1 / fw <1, of which R1
The small camera zoom device according to claim 1, wherein is the radius of curvature of the first optical surface, fw is the focal length at the wide-angle end of the zoom lens of the camera, and f1 is the focal length of the second lens system.