Focus detecting device

• US 4,566,773 A
• Filed: 06/20/1984
• Issued: 01/28/1986
• Est. Priority Date: 06/24/1983
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kaneda, Naoya
• Primary Examiner(s): Perkey, William B.
• Application Number:
  US06/622,686
• Time in Patent Office: 587 Days
• Field of Search: 354/403, 354/165
• US Class Current: 396/80
• CPC Class Codes: G02B 7/30 using parallactic triangle with a base line

Abstract

A focus detecting device with two optical systems for measuring an object distance, having their optical axes separated at a base line length. One of the axes lies within a photographic objective lens system and the other lies outside of it. The optical axis of the former is offset from the optical axis of the photographic lens system in a direction away from the optical axis of the latter.

Claims

1. A lens mounting comprising:

(a) a taking lens including a focusing lens and a lens holder for said taking lens;

(b) light emitting means having a light emitting element housed within said lens holder and a reflection mirror for reflecting the light beam projected from said light emitting element toward an object to be photographed, wherein said reflection mirror is placed at a position opposing said light emitting element, sandwiching the optical axis of said focusing lens therebetween, and the optical axis of projected light beam, after being reflected, is offset from the optical axis of the focusing lens; and

(c) means for receiving a reflected light beam which has also been reflected by the object, said light receiving means being placed at a position at the outside of an effective diameter of said taking lens and at a side of the optical axis of said taking lens at which said light emitting element is placed.

3. A lens mounting according to claim 1 or 2, wherein said light emitting means and said light receiving means are positioned in such a manner that a segment of line connecting the center of the light emitting element constituting said light emitting means and the center of said reflection mirror and a segment of line connecting the center of said light receiving means and the center of said reflection mirror are offset from each other.

4. A lens mounting according to claim 3, in which said light receiving means includes a half divided light receiving element and when an angle formed by a segment of line perpendicular to the dividing line of said light receiving element and a line perpendicular to the optical axis of the lenses is expressed by an angle θ

3 at a long focal length of a zoom lens consisting of said focusing lens and variator lens and by an angle θ

4 at a short focal length of the same, said light receiving elements are placed between said angle θ

3 and said angle θ

4.

2. A lens mounting comprising:

(a) a focusing lens, a variator lens and a lens holder for housing each one of said lenses;

(b) light emitting means comprising a light emitting element, a projection lens and a reflection mirror, each member of said light emitting means being placed within said lens holder and on a camera side of said focusing lens and said variator lens, and said light emitting element and said reflection mirror opposing each other with the optical axis of said lenses therebetween, whereby a light beam reflected by said reflection mirror advances toward an object in a path being offset from said optical path of the lenses; and

(c) means for receiving a reflected light beam which has also been reflected from the object, said light receiving means being positioned outside said lens holder and being provided on the same side of said optical axis of the lenses on which the light emitting element is positioned.