Automatic focusing device

• US 5,053,798 A
• Filed: 08/28/1989
• Issued: 10/01/1991
• Est. Priority Date: 01/14/1987
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tanaka, Tsunefumi, Chigira, Tatsuo, Ohara, Tsunemasa
• Primary Examiner(s): Adams, Russell E.
• Application Number:
  US07/398,332
• Time in Patent Office: 764 Days
• Field of Search: 354/400, 354/402, 354/195.1, 354/195.12, 354/286
• US Class Current: 396/135
• CPC Class Codes: G02B 7/102 controlled by a microcomputer cameras with interchangeable lenses G03B17/14

Abstract

An automatic focusing device for performing focus detection through an objective optical system, and adjusting the focusing position of the objective optical system in accordance with the detection result, wherein the attachment or detachment of an optical element for changing the focal length of the objective optical system is detected, and the speed of the drive source is changed depending on the detection result.

Claims

1. An automatic focus adjustment device comprising:

an objective optical system;

focus detecting means for repeatedly detecting a focus state of said objective optical system by using light passing through said objective optical system;

optical means for changing the focal length of said objective optical system;

attachment detecting means for detecting whether or not said optical means has been inserted in the optical path of said objective optical system;

focusing means for performing focusing of a composite system having said optical system and said optical means;

a driving source motor for driving said focusing means; and

means for discriminating the attachment of said optical means on the basis of an output of said attachment detecting means, and for changing a motor speed of said driving source motor depending on a property of said optical means in accordance with the focus state detected by said focus detecting means for compensating for a change in the movement rate of the image plane caused by the attachment of said optical means.

2. A device according to claim 1, wherein said optical means is a conversion lens.

3. A device according to claim 2, wherein said conversion lens is an extender.

4. A device according to claim 2, wherein said conversion lens is a reducer.

5. A device according to claim 2, wherein said optical means is attached in between said objective optical system and said focus detecting means.

6. A device according to claim 1, wherein said optical means is a closeup lens.

7. A device according to claim 6, wherein said optical means is attached to the object side of said objective optical system.

8. A camera system comprising:

a camera body;

a photographic lens releasably attached to said camera body;

focus detecting means provided in said camera body to repeatedly detect a focus state of said photographic lens;

a conversion lens releasably attached in between said photographic lens and said camera body;

detecting means for detecting the attachment of said conversion lens;

focusing means for performing focusing of said photographic lens or a composite system of said photographic lens and said conversion lens;

said photographic lens having a driving source motor for driving said focusing means; and

means electrically connected to said detecting means and responsive to attachment of said conversion lens for changing a motor speed of said driving source motor in accordance with an optical value of said photographic lens for compensating for a change in the movement rate of the image plane caused by the attachment of said optical means.

9. A camera system according to claim 8, wherein said conversion lens is an extender.

10. A camera system according to claim 8, wherein said conversion lens is a reducer.