JPH03196109A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a large zoom ratio by a miniature zoom lens by varying power of the image of an object to be photographed by moving the rear group lens to an image forming lens of the front group from a state that the photoelectric converting surface comes to the focal position of image side of the front group lens. CONSTITUTION:Variable power of an image of an object to be photographed is executed by moving the rear group lens 3 to an image forming lens of the front group from a state that the photoelectric converting surface is positioned between two principal planes of the rear group lens 3 in a zoom lens constituted of two groups of the image forming lens 1 of the front group and the lens of the rear group, and also, the photoelectric converting surface comes to a focal position of the image side of the front group lens 1. Also, the photoelectric converting surface is moved to the focused position of the lens system moved by displacement of the rear group lens 3. In such a way, a miniature zoom lens whose zoom ratio is large and whose constitution in simple can be obtained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to zoom lenses, particularly television cameras,
This invention relates to a zoom lens used in camera-integrated VTRs, etc.

(Prior Art) Various types of variable focus lenses have been known, including those with a two-group configuration, three-group configuration, four-group configuration, and five-group configuration.

(Problems to be Solved by the Invention) In recent years, consumer color television cameras and camera-integrated VTRs have become widespread, and these devices often use zoom lenses as imaging optical systems.

However, zoom lenses that have traditionally been used in consumer color television cameras and camera-integrated VTR imaging optical systems have been large and complicated in construction, so zoom lenses that are compact and have a large zoom ratio It was hoped that a lens would appear.

(Means for Solving the Problems) The present invention is a zoom lens having a two-group configuration of an imaging lens in a front group and a lens in a rear group, in which a photoelectric conversion surface is located between two principal planes of the rear group lens. Further, the magnification of the subject image is changed by moving the rear group lens toward the front group imaging lens from the state where the photoelectric conversion surface is at the focal position on the image side of the front group lens. A zoom lens, and a zoom lens having a two-group configuration of a front group imaging lens and a rear group lens,
The photoelectric conversion surface is located between the two principal planes of the rear group lens, and the photoelectric conversion surface is at the focal position on the image side of the front group lens, and then the rear group lens is moved to the front group imaging lens. To provide a zoom lens in which a photoelectric conversion surface is moved so as to change the magnification of a subject image by moving it toward , and at the same time maintain a single in-focus state.

(Function) This is a two-group zoom lens consisting of a front group imaging lens and a rear group lens, and a photoelectric conversion surface is located between the two principal planes of the rear group lens, and the photoelectric conversion surface is located between the two principal planes of the rear group lens. From the value of the composite focal length of the lens system when the front group imaging lens is at its focal position on the image side, that is, when the rear group lens does not substantially exhibit any lens action, the rear group lens is moved to the front. The value of the composite focal length of the front group imaging lens and the rear group lens obtained by moving toward the imaging lens of the group,
A zoom lens with a large zoom ratio is constructed. Further, the photoelectric conversion surface is moved to the focal position of the lens system, which is moved by the displacement of the rear group lens.

(Example) Hereinafter, specific details of the zoom lens of the present invention will be explained in detail with reference to the accompanying drawings. Figures 1 and 2 show the zoom lens of the present invention, that is, a zoom lens with a two-group configuration of an imaging lens in the front group and a lens in the rear group, and photoelectric conversion is performed between the two principal planes of the rear group lens. The object image is magnified by moving the rear group lens toward the front group imaging lens from a state in which the photoelectric conversion surface is located at the same position and the photoelectric conversion surface is at the focal position on the image side of the front group lens. FIG. 3 is a diagram showing the construction principle and operation principle of different embodiments of the zoom lens.

The embodiment shown in FIG. 1 includes an imaging lens 1 and a convex lens 3 in the front group.
FIG. 2 is a zoom lens that is composed of a front group imaging lens 1 and a rear group lens that is a concave lens 4. A component designated by the drawing numeral 2 in FIG. 2 is a photoelectric converter such as a two-dimensional CCD image sensor.

FIG. 1(a) and FIG. 2(a) show that the photoelectric conversion surface of the photoelectric converter 2 is located at the focal position on the image side of the imaging lens 1 of the front group, and the photoelectric conversion A portion between the object-side principal plane and the image-side principal plane of the rear group lens 3 (or 4) is located at the position of the photoelectric conversion surface of the device 2.

As shown in FIG. 1(a) and FIG. 2(a), the photoelectric conversion surface of the photoelectric converter 2 is located at the focal position on the image side of the imaging lens 1 of the front group. In addition, when the portion between the object-side principal plane and the image-side principal plane of the rear group lens 3 (or 4) is located at the position of the photoelectric conversion surface of the photoelectric converter 2, , rear lens group 3 (or 4
) is in a state where it does not substantially exhibit lens action, so when the convex lens 3 is used as the rear group lens as in the embodiment shown in FIG. 1, (a) in FIG.
), the zoom lens has the longest focal length f! (
The focal length of the front group imaging lens 1 is fl).

Furthermore, when the convex lens 4 is used as the rear group lens as in the embodiment shown in FIG.
l (focal length fl of the imaging lens 1 of the front group).

Next, as shown in FIG. 1 (b) and FIG. 2 (b), the rear group lens 3 (or 4) is fixed as shown in FIG. If the zoom lens is moved from the state where it is in the direction of the front group imaging lens 1, the focal length of the zoom lens becomes the composite focal length of the front group imaging lens 1 and the rear group lens 3 (or 4). The value changes to .

In the embodiment shown in the first diagram, the focal length of the zoom lens changes to be smaller than the focal length f1 of the imaging lens 1 of the front group according to the amount of forward movement of the rear group lens 3,
Further, in the embodiment shown in the second figure, the focal length of the zoom lens changes to be larger than the focal length f1 of the imaging lens 1 of the front group according to the amount of forward movement of the rear group lens 4, and Both of the zoom lenses shown in the figure and the second figure have a large zoom ratio.

As described above, the position of the rear group lens 3 (or 4) is moved from the position shown in FIG. 1(a) or FIG. 2(a) toward the front group imaging lens 1. Even if the focal plane of the lens system is at the position of the photoelectric conversion surface of the photoelectric converter 2 shown in (a) of FIG.
In order to position the photoelectric conversion surface of the photoelectric converter 2 as shown in ), for example, the front group imaging lens 1 must be moved in accordance with the movement of the rear group lens 3 (or 4) described above. It is necessary to move as shown in FIG. 1(b) or FIG. 2(b).

However, while the front group imaging lens 1 remains at the position shown in FIG. 1(a) or the position shown in FIG. 2(a), the rear group lens 3 (or Even if the position of 4) is moved from the position shown in FIG. 1(a) or FIG. 2(a) toward the front group imaging lens 1, the focal point of the lens system The photoelectric converter 2 may be moved so that the photoelectric conversion surface of the photoelectric converter 2 is located on the surface.

In this state, the positions of the front group p imaging lens 1 and the photoelectric converter 2 are the same as that of the front group imaging lens 1' and the photoelectric converter shown by dotted lines in FIG. 1(b) or FIG. 2(b). converter 2'
This is an example.

Also due to the displacement of the rear group lens 3 (or 4) described above,
The position of the photoelectric converter 2 is adjusted by the dotted frame shown in (b) in FIG. 1 and (b) in FIG. 2' position, or the position of the front group imaging lens 1 as shown in Fig. 1 (
By moving the imaging lens 1 to the position of the front group imaging lens 1 shown by the solid line in FIG. 2(b) and (b) of FIG. This can be easily realized by the operation of an automatic control system configured to move the position of the photoelectric converter to such a state.

(Effects of the Invention) As is clear from the above detailed explanation, the zoom lens of the present invention, which has a two-group configuration consisting of a front group imaging lens and a rear group lens, has a distance between the two main planes of the rear group lens. A state in which the photoelectric conversion surface is located at and the photoelectric conversion surface is the focal position on the image side of the imaging lens of the front group, that is,
The front group imaging lens and the front group imaging lens obtained by moving the rear group lens toward the front group imaging lens from the value of the composite focal length of the lens system in a state where the rear group lens does not substantially exhibit any lens action. Depending on the value of the combined focal length with the rear group lens, it is possible to construct a zoom lens with a larger zoom ratio than a conventional zoom lens with a two-group configuration. By using the automatic position control method used, the photoelectric conversion surface can be easily moved to the focusing position of the lens system that moves by the displacement of the rear group lens, and according to the present invention, the zoom ratio is large and the configuration is A simple and compact zoom lens can be easily provided.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing the constituent elements and operating principles of different embodiments of the zoom lens of the present invention. 1... Front group imaging lens, 2... Photoelectric converter, 3° 4... Rear group lens,

Claims (1)

[Scope of Claims] 1. A zoom lens with a two-group configuration of an imaging lens in the front group and a lens in the rear group, in which a photoelectric conversion surface is located between the two principal planes of the rear group lens, and A zoom lens 2 that changes the magnification of a subject image by moving the rear group lens toward the front group imaging lens from a state in which the photoelectric conversion surface is at the focal position on the image side of the front group lens; The zoom lens 3 according to claim 1, wherein the rear group lens is a convex lens, the zoom lens 4 according to claim 1, wherein the rear group lens is a concave lens, and the two-group configuration of a front group imaging lens and a rear group lens. A zoom lens in which the photoelectric conversion surface is located between the two principal planes of the rear group lens, and the photoelectric conversion surface is the focal position on the image side of the front group lens. A zoom lens that changes the magnification of the subject image by moving the lens toward the front group imaging lens, and at the same time moves the photoelectric conversion surface so that the in-focus state is maintained.