Camera having focus detection device

• US 4,333,717 A
• Filed: 12/31/1980
• Issued: 06/08/1982
• Est. Priority Date: 07/14/1977
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tamura, Shuichi
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US06/221,701
• Time in Patent Office: 524 Days
• Field of Search: 354/25, 354/60 R, 354/195, 354/196, 354/198, 354/31, 355/56, 352/140
• US Class Current: 396/98
• CPC Class Codes: G02B 7/30 using parallactic triangle with a base line

Abstract

A camera having a focus detecting device for automatically detecting a condition of sharpest focus. According to an improvement of the invention, when the brightness level of an object of principal photographic interest becomes so low as not to permit satisfactory operation of the focus detecting device, or when the actual voltage of a battery falls below a satisfactory operating level for the device, a supplementary device can be rendered operative to control setting of a photo-taking lens independently of the focus detecting device, thereby the camera can be focused at an appropriate distance depending upon the size of diaphragm aperture, namely, in a pan-focus position.

According to a further improvement of the invention, an exposure control apparatus in the camera is made associated with the aforesaid two devices in a manner to be rendered operative in response to an accomplishment of setting the taking lens.

Claims

1. A device comprising:

(A) lens means adjustable along an optical axis for focusing on an object;

(B) distance detecting means for detecting the distance of the object and producing an electrical indication indicative of the object distance;

(C) first indicating means correlated with said lens means for producing an electrical indication indicative of the position of the lens means on the optical axis;

(D) second indicating means for providing an electrical indication indicative of at least one limited distance;

(E) selecting means for automatically selecting one of the electrical indications produced by said distance detecting means and the electrical indication provided by said second indicating means; and

(F) output indicating means response to the electrical indication selected by said selecting means and to the electrical indication produced by said first indicating means for producing an output indication which is available for setting the lens means to a position at which the lens means is focused to the distance indicated by the electrical indication selected by the selecting means.

2. A device according to claim 1, further comprising:

brightness detecting means for detecting the brightness of the object and producing a first characteristic output when the object brightness is above a predetermined brightness level and producing a second characteristic output when the object brightness is below a predetermined brightness level;

said selecting means being responsive to said brightness detecting means for selecting the electrical indication produced by said distance detecting means in response to the first characteristic output, and selecting the electrical indication provided by said second indicating means in response to the second characteristic output.

3. A device according to claims 1 or 2, wherein said second detecting means is arranged to provide the electrical indication as an electrical indication which indicates a hyper-focal distance for approximate focus of the lens means to the object.

4. An automatic focusing camera comprising:

an automatic focusing system for performing one of two different focus control functions, the first of which focuses an objective on an object more accurately than the second, and the second of which approximately focuses the objective on the object as an alternative to the first; and

an exposure system including;

exposure means for exposing a film to object light coming through the objective; and

exposure control means associated with said automatic focusing system for controlling the exposure operation of said exposure means and for prohibiting the exposure operation of the exposure means until at least one of said first and second focus control functions is performed by the automatic focusing system.

5. An automatic focusing camera according to claim 4, further comprising:

brightness detecting means for detecting the brightness of the object and controlling said automatic focusing system according to the detected object brightness and for causing the focusing system to perform the first focus control function when the object brightness is above a predetermined brightness level and causing the focusing system to perform the second focus control function when the object brightness is below a predetermined level.

6. An automatic focusing camera according to claims 4 or 5, further comprising:

power source circuit means for connection to a power source; and

voltage detecting means for detecting the voltage level of the power provided by said power source circuit means and for causing the focusing system to perform the first focus control function when the voltage level of the power is above a predetermined level and causing the focusing system to perform the second focus control function when the object brightness is below a predetermined level.