Prism optical system, prism optical system-incorporated image display apparatus, and prism optical system-incorporated imaging apparatus

• US 10,444,481 B2
• Filed: 11/08/2017
• Issued: 10/15/2019
• Est. Priority Date: 05/11/2015
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Takahashi, Koichi
• Primary Examiner(s): Harrington, Alicia M
• Application Number:
  US15/806,463
• Publication Number:
  US 20180067289A1
• Time in Patent Office: 706 Days
• CPC Class Codes: G02B 17/086 wherein the system is made of a single block of optical material, e.g. solid catadioptric systems
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/04 Prisms

Abstract

A prism optical system has an optical element that includes, a first surface that defines a transmitting surface as an entrance surface and an internal reflecting surface as well, a second surface that defines an internal reflecting surface in opposition to the first surface, a third surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the second surface, a fourth surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the third surface and an internal reflecting surface closest to the image plane as well, and a fifth surface that defines a transmitting surface adjacent to the first surface and in opposition to the fourth surface; the fourth surface is defined by a rotationally asymmetric surface having a negative power in the Y-Z plane and a positive power in the X-direction perpendicular to the Y-Z plane.

Claims

1. A prism optical system comprising:

an optical element that includes at least five optical surfaces, each having an optical action, wherein at least three out of the at least five optical surfaces are rotationally asymmetric surfaces and one of two surfaces on which light is incident or out of which light exits has one transmission and at least one internal reflection;

in a light ray traveling from an entrance pupil toward an image plane through the optical element, at least a portion of a reflecting surface closest to the image plane along an optical path has a negative power;

the optical element comprises, in order along a path taken by light that enters and exits out of the optical element,

a first surface that defines a transmitting surface as an entrance surface and an internal reflecting surface as well,

a second surface that defines an internal reflecting surface in opposition to the first surface,

a third surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the second surface,

a fourth surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the third surface and an internal reflecting surface closest to the image plane as well, and

a fifth surface that defines a transmitting surface adjacent to the first surface and in opposition to the fourth surface; and

given that a Z-axis positive direction is defined by a direction along a direction of travel of a center chief ray, perpendicular to a plane that defines the entrance pupil, from one point included in a dummy plane that is an origin through the center of the entrance pupil, a Y-Z plane is defined by a plane including the Z-axis and the center of the image plane, and a Y-axis positive direction comes close to a direction from the origin toward the center of the image plane, and an X-axis positive direction is defined by a direction that forms a right-handed orthogonal coordinate system with the Y-axis and the Z-axis,

the fourth surface is defined by a rotationally asymmetric surface having a negative power in the Y-Z plane and a positive power in the X-direction perpendicular to the Y-Z plane.

2. The prism optical system according to claim 1, wherein the following condition (1) is satisfied:

−

4<

cy(x,y)/cx(x,y)<

−

0.01 

 

(1)

where cy(x, y) stands for a Y-direction curvature of a position of the fourth surface where the center chief ray is reflected off, and

cx(x, y) stands for an X-direction curvature of a position of the fourth surface through which the center chief ray transmits,

given the surface shape defined by f(x, y) in the position (x, y), the X-direction curvature cx(x, y) and the Y-direction curvature cy(x, y) in the position (x, y) are here intended to the following

3. The prism optical system according to claim 2, wherein the third surface is defined by a rotationally asymmetric surface.

4. The prism optical system according to claim 1, wherein total reflection is applied to at least one internal reflection of light by the first surface.

5. The prism optical system according to claim 1, wherein the first surface is defined by a rotationally asymmetric surface.

6. The prism optical system according to claim 1, wherein the first surface has a negative power in the Y-Z plane.

7. The prism optical system according to claim 1, wherein the second surface is defined by a rotationally asymmetric surface.

8. The prism optical system according to claim 1, wherein the second surface has a positive power in the Y-Z plane.

9. An image display apparatus incorporating the prism optical system according to claim 1,

wherein an image display device is located in opposition to the fifth surface of the optical element, and

the eyes of a viewer are positioned in opposition to a transmitting area of the first surface to present an enlarged virtual image to the viewer.

10. An imaging apparatus incorporating the prism optical system according to claim 1,

wherein an imaging device is located in opposition to the fifth surface of the optical element, and

an aperture stop is located in front of and in the vicinity of a transmitting surface of the first surface thereby taking an external-world image.

11. A prism optical system comprising:

an optical element that includes at least five optical surfaces, each having an optical action, wherein at least three out of the at least five optical surfaces are rotationally asymmetric surfaces and one of two surfaces on which light is incident or out of which light exits has one transmission and at least one internal reflection;

in a light ray traveling from an entrance pupil toward an image plane through the optical element, at least a portion of a reflecting surface closest to the image plane along an optical path has a negative power;

the optical element comprises, in order along a path taken by light that enters and exits out of the optical element,

a first surface that defines a transmitting surface as an entrance surface and an internal reflecting surface as well,

a second surface that defines an internal reflecting surface in opposition to the first surface,

a third surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the second surface,

a fourth surface that defines an internal reflecting surface in opposition to the first surface and adjacent to the third surface and an internal reflecting surface closest to the image plane as well, and

a fifth surface that defines a transmitting surface adjacent to the first surface and in opposition to the fourth surface; and

given that the Z-axis positive direction is defined by a direction along a direction of travel of a center chief ray, perpendicular to a plane that defines the entrance pupil, from one point included in a dummy plane that is an origin through the center of the entrance pupil, the Y-Z plane is defined by a plane including the Z-axis and the center of the image plane, and a Y-axis positive direction comes close to a direction from the origin toward the center of the image plane, and an X-axis positive direction is defined by a direction that forms a right-handed orthogonal coordinate system with the Y-axis and the Z-axis,

the fourth surface is defined by a rotationally asymmetric surface having a negative power in the Y-Z plane and a negative power in the X-direction perpendicular to the Y-Z plane.