US 4,043,642 AGranted

Zoom lens system having electrical control of moving elements

AssigneeCanon Kabushiki Kaisha

InventorsRyusho Hirose, Takao Tsuji

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Abstract

From an object side, there are a fixed lens, a first movable lens, a second movable lens, and a fixed lens being positioned in that order, wherein the first movble lens is coupled with a first position detecting means and the second movable lens is coupled with a second position detecting means, and at the same time it is coupled with a lens shifting means which is controlled by the above mentioned two detecting means. For photographing which involves zooming, first the second movable lens is shifted for focusing. Next, as the first movable lens is shifted, the amount of shifting is detected by the first detecting means and then the second movable lens is shifted based on the detected value of the same. The amount of shifting of said second movable lens is determined by a functional equation which has been set as the optical system is designed, while the position adjustment of the second movable lens is controlled by the lens shifting means and the second detecting means. While magnification variation is performed as a result of shifting of the first movable lens and of the second movable lens, there will be no shifting of image in an image.

Claims9

Dependent claims

A zoom lens system without a single focusing lens at the front part of the lens system comprising:

a variation movable lens group relating to the focal length of the whole optical system and being capable of moving along the optical axis;
a compensation movable lens relating to focusing and being capable of moving along the optical axis;
a fixed lens group in front of the movable lens groups;
a diaphragm;
a fixed lens group in front of a photosensitive material plane;
a first detecting means for detecting the distance, c, between the actual position of said variation movable lens group and the basic position of magnification variation in order to supply a magnification variation signal;
a second detecting means to detect the distance, a, between the actual position of said compensation movable lens group and the basic position of compensation in order to provide a compensation signal, wherein the basic position of compensation is determined as a position in which focus is on an object at an infinite position when said compensation movable lens group is at said basic position and variation movable lens group is fixed at said basic position of magnification variation;
an operation means responsive to said compensation signal and said magnification signal for providing a control signal corresponding to the desired distance, b, between the position of said compensation lens group and said basic position of compensation, said operation means providing said signal in accordance with a predetermined functional relationship of distances c and a of the variation movable lens group and said compensation movable lens group;
and
a setting means to set said compensation movable lens group at a position on the optical axis in response to said control signal.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/627,867Filed 31 Oct 1975 · continuation
Priority: JA 48-263436 Mar 1973
Granted: 23 Aug 1977
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G02B 15/22
By axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of…:…
G02B 7/282
Systems for automatic generation of focusing signals: autofocusing of zoom lenses
G02B 15/144109
The first group being positive: arranged +--+
G03B 17/14
With means for supporting objectives, supplementary lenses, filters, masks, or turrets: interchangeably