# US 5,708,869 A · Image magnification control device for a camera

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- Number: US 5,708,869 A
- Document ID: US5708869A
- Status: Granted
- Kind: A
- Application number: 08/701,759
- Filed: 1996-08-22
- Granted: 1998-01-13
- Earliest claimed: 1988-09-22
- Assignees: Asahi Kogaku Kogyo Kabushiki Kaisha
- Inventors: Noboru Suzuki; Shigeo Toji; Masahiro Kawasaki
- Web page: https://patentgrep.com/patent/US5708869A

## CPC

- G02B 7/102: {controlled by a microcomputer (cameras with interchangeable lenses G03B17/14)}
- G02B 7/282: {Autofocusing of zoom lenses}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An image magnification control device for a camera. Control focal length required to maintain an image magnification constant is computed based upon defocus information detected by analyzing a light that passes through a photographic lens. In case a focal length of the photographic lens moves out of a range wherein the set image magnification can be obtained, various options, such as a shutter-release lock operation, can be executed depending upon the chosen design of the camera.

## Claims

### Claim 1

An image magnification control device for a camera, said device comprising:
means for effecting image magnification control of the camera;
means for monitoring the level of contrast of an object to be photographed; and
means for disabling said image magnification control effecting means until such time as the monitored level of contrast of the object to be photographed reaches a prescribed minimum level.

### Claim 2 (depends on 1)

The image magnification control device according to claim 1, wherein said effecting means effects image magnification control of the camera based upon one or more predetermined measured values.

### Claim 3

An image magnification control device for a camera, said device comprising:
means for effecting image magnification control of the camera;
means for determining if the camera is in a macro mode; and
means for disabling said image magnification control effecting means until such time as the camera is determined to be taken out of the macro mode.

### Claim 4 (depends on 3)

The image magnification control device according to claim 3, wherein said effecting means effects image magnification control of the camera based upon one or more predetermined measured values.