Rangefinding device for camera

• US 5,870,636 A
• Filed: 09/05/1997
• Issued: 02/09/1999
• Est. Priority Date: 09/09/1996
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Ito, Kazumi, Sugita, Yukihiko
• Primary Examiner(s): Perkey, W. B.
• Application Number:
  US08/924,750
• Time in Patent Office: 522 Days
• Field of Search: 396/106, 396/109, 396/110, 396/111, 396/120, 356/3.01-3.08
• US Class Current: 396/106
• CPC Class Codes: G01C 3/085 with electronic parallax measurement
• CPC Class Codes: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40

Abstract

A rangefinding device for a camera, in which a light projecting unit for projecting near-infrared light to an object and a light receiving unit for receiving object-reflected light reflected from an object are provided in such a manner as to be nearly in parallel with each other. The light receiving unit is provided with: a prism having a total reflection surface for reflecting almost all of object-reflected light having been incident thereon; and a light receiving element for receiving object-reflected light that is reflected by this total reflection surface of the prism. Further, the total reflection surface of the prism is formed so that a sum of an angle of incidence and an angle of reflection of object-reflected light reflected by the total reflection surface of this prism is greater than 90° degrees.

Claims

1. A rangefinding device for a camera, comprising:

a prism having a lens portion at least one of an incident surface receiving light reflected from an object and an exit surface and having a total reflection surface which reflects light reflected from a image entering said prism said reflection surface formed so that a sum of an angle of incidence and an angle of reflection of object-reflected light is more than 90°

degrees from said reflection surface; and

a light receiving element for receiving object-reflected light that is reflected by said prism and exits through said exit surface.

2. The rangefinding device for a camera, according to claim 1, wherein a light receiving surface of said light receiving element is inclined at a predetermined angle to an incident optical axis of an imaging lens.

3. The rangefinding device for a camera, according to claim 2, wherein the predetermined angle is an angle at which nearly all of luminous fluxes of light reflected from a reflection surface of said prism are able to be received by said light.

15. A rangefinding device for a camera according to claim 1 wherein the prism is a unitary, one-piece member.

4. A rangefinding device for a camera, comprising:

a prism having a reflection surface formed so that a sum of an angle of incidence and an angle of reflection of object-reflected light is more than 90°

degrees; and

a light receiving element for receiving object-reflected light that is reflected by said prism said prism having a groove portion that is provided at a position facing said reflection surface for preventing light, which is reflected from an object, from being incident directly upon said light receiving element.

5. The rangefinding device for a camera, according to claim 4, wherein a section of said groove portion is shaped like a letter "V".

6. A rangefinding device for a camera, comprising:

light projecting means for projecting near-infrared light onto an object;

a prism having a lens portion at at least one of an incident surface receiving light reflected from an object and an exit surface and having a reflection surface which reflects light reflected by an image and entering said prism, said reflection surface being formed so that a sum of an angle of incidence and an angle of reflection of object-reflected light, which is reflected from the object, is more than 90°

degrees; and

a light receiving element for receiving object-reflected light that is reflected by said prism and exiting from said exit surface.

7. (Amended) The rangefinding device for a camera, according to claim 6, wherein said light projecting means comprises:

a light projecting lens provided in such a manner as to have it central axis nearly parallel with a forward portion of said prism; and

a light projecting element for emitting near-infrared light.

8. The rangefinding device for a camera, according to claim 6, wherein said light receiving element is placed diagonally behind said light projecting element.

9. The rangefinding device for a camera, according to claim 7, wherein said prism has a groove portion that is provided at a position facing said reflection surface for preventing light, which is reflected from the object, from being incident directly upon said light receiving element.

10. The rangefinding device for a camera, according to claim 9, wherein a section of said groove portion is shaped like a letter "V".

11. A rangefinding device having a finder optical system for a camera, comprising:

a light projecting lens formed in such a manner as to be integral with a predetermined lens provided in said finder;

a light projecting element for projecting near-infrared light onto an object through said light projecting lens;

a prism which is substantially parallel to said light projecting lens and has a reflection surface formed so that a sum of an angle of incidence and an angle of reflection of object-reflected light is an obtuse angle; and

a light receiving element which is placed diagonally behind said light projecting element and receives object-reflected light that is reflected by said prism.

12. The rangefinding device according to claim 11, wherein said prism has a groove portion that is provided at a position facing said reflection surface for preventing light, which is reflected from the object, from being incident directly upon said light receiving element.

13. The rangefinding device for a camera, according to claim 12, wherein a section of said groove portion is shaped like a letter "V".

14. A rangefinding device for a camera, comprising:

light projecting means for projecting light onto an object, said light projecting means having a light emitting element for emitting light and a light projecting lens for projecting the emitted light onto an object; and

light receiving means for receiving light reflected from an object, said light receiving means comprising a light receiving element for receiving light reflected from an object and a light-receiving optical element, said light receiving element being placed nearly behind said light emitting element, said light-receiving optical element having a forward portion placed adjacent to a side of said light receiving element and an integral rearward portion inclined at an angle to said forward portion.

16. A rangefinding device for a camera according to claim 14 wherein said light-receiving optical element is a prism having a lens portion formed at at least one of an incident surface and an exit surface.