Image-forming optical system

• US 6,900,950 B2
• Filed: 10/24/2003
• Issued: 05/31/2005
• Est. Priority Date: 12/25/2000
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Nagata, Tetsuo
• Primary Examiner(s): Spector, David N.
• Application Number:
  US10/691,664
• Publication Number:
  US 20040090683A1
• Time in Patent Office: 585 Days
• Field of Search: 359/720, 359/726, 359/727, 359/793, 359/833, 359/834, 359/630, 359/631
• US Class Current: 359/720
• CPC Class Codes: G02B 13/0015 characterised by the lens design
• CPC Class Codes: G02B 13/005 having spherical lenses only
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/0065 having a beam-folding prism or mirror
• CPC Class Codes: G02B 13/007 the beam folding prism having at least one curved surface
• CPC Class Codes: G02B 17/0832 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/0848 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/086 wherein the system is made of a single block of optical material, e.g. solid catadioptric systems

Abstract

A high-performance and low-cost image-forming optical system has a reduced number of constituent optical elements and is made extremely thin, particularly in a direction perpendicular to an image pickup device, by folding an optical path using only three reflecting surfaces. The image-forming optical system has a front unit including a first prism 10, an aperture stop 2, and a rear unit including a second prism 20. The first prism 10 has a first transmitting surface 11, a first reflecting surface 12, and a second transmitting surface 13. The second prism 20 has a first transmitting surface 21, a first reflecting surface 22, a second reflecting surface 23, and a second transmitting surface 24. An optical path incident on the first reflecting surface 22 and an optical path exiting from the second reflecting surface 23 intersect each other. The first reflecting surface 12 of the first prism 10 and the first and second reflecting surfaces 22 and 23 of the second prism 20 have a curved surface configuration that gives a power to a light beam. The curved surface configuration is a rotationally asymmetric surface configuration that corrects aberrations due to decentration.

Claims

1. An image-forming optical system, comprising a first prism, a second prism and an aperture stop interposed between the first prism and the second prism, wherein:

said first prism comprises;

a first-first transmitting surface through which a light beam transmits,

a first-second reflecting surface for reflecting a light beam, and

a first-third transmitting surface through which a light beam transmits, wherein said first-first transmitting surface, said first-second reflecting surface and said first-third transmitting surface are arranged in this order in an optical path between entrance of a light beam from said first prism and emergence of said light beam from said first prism,

said second prism comprises;

a second-first transmitting surface through which a light beam transmits,

a second-second reflecting surface for reflecting a light beam,

a second-third reflecting surface for reflecting a light beam, and

a second-fourth transmitting surface through which a light beam transmits, wherein;

said second-first transmitting surface, said second-second reflecting surface, said second-third reflecting surface and said second-fourth transmitting surface are arranged in this order in an optical path between entrance of a light beam in said second prism and emergence of said light beam from said second prism,

said second-first transmitting surface is opposed to said second-second reflecting surface,

said second-third reflecting surface is opposed to said second-fourth transmitting surface,

said first-second reflecting surface, said second-second reflecting surface and said second-third reflecting surface have each a rotationally asymmetric surface shape for giving power to a light beam,

said first prism has an equal sign of power in two orthogonal directions,

said second prism has an equal sign of power in two orthogonal directions, and

the image-forming optical system does not form an intermediate image.

2. An electronic camera, comprising:

an image-forming optical system as recited in claim 1;

an image pickup device placed in an image plane formed by said image-forming optical system;

a recording medium for recording image information received by said image pickup device; and

an image display device that receives image information from one of said recording medium and said image pickup device to form an image for observation.

3. A cellular phone, comprising:

an input unit for inputting information;

a display unit for displaying the information;

a voice input unit;

a voice output unit;

an antenna; and

an image pickup optical system for imaging an object;

wherein said image pickup optical system has said image-forming optical system according to claim 1.