Image enhancement and aberration corrections in a small real image projection system

• US 6,935,747 B2
• Filed: 03/13/2003
• Issued: 08/30/2005
• Est. Priority Date: 04/27/1999
• Status: Expired due to Fees

• Current Assignee: Optical Products Development Corporation
• Original Assignee: Optical Products Development Corporation
• Inventors: Westort, Kenneth S., Robinson, Douglas L.
• Primary Examiner(s): Nguyen, Judy
• Assistant Examiner(s): SEVER, ANDREW T
• Application Number:
  US10/388,062
• Publication Number:
  US 20030210380A1
• Time in Patent Office: 901 Days
• Field of Search: 353/7, 353/98, 353/28, 353/30, 353/37, 353/77, 353/10, 353/99, 353/74, 353/78, 359/629, 359/462, 359/478, 359/479, 359/630, 359/631, 359/477, 359/13, 359/483, 359/850, 359/857, 359/858, 359/864, 359/633, 349/67, 349/11, 463 30- 34
• US Class Current: 353/28
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G02B 17/0856 comprising a refractive element with a reflective surface, the reflection taking place inside the element, e.g. Mangin mirrors
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 30/56 by projecting aerial or floating images
• CPC Class Codes: G07F 9/02 Devices for alarm or indication, e.g. when empty; Advertising arrangements in coin-freed apparatus alarms or warning devices indicating the interruption of flow to be metered G07F15/10
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence

Abstract

An improved real image projection system comprises, in the primary configuration, a tilted mirror to eliminate ghost reflections, and a unique arrangement allowing the introduction of a second background image without a 50%/50% beamsplitter, while providing system transmission of approximately 50%. A secondary configuration incorporates an elliptical or aspheric curved mirror designed to simulate the surface of a spherical curve when light strikes the elliptical surface at an angle equal to the elliptical angle of the curved mirror. In a third configuration, a single curved mirror has two different optical surfaces of revolution, one on the convex surface and one on the concave surface. The concave surface is much like that of a Mangin lens, but it has an aspheric surface of revolution, optimized to reduce spherical aberrations over a larger area offset from the optical axis.

Claims

1. A real image projection system, comprising:

a) a curved mirror, mounted with an optical axis of said curved mirror at a tilted angle, relative to an imagine axis of said image projection system;

b) a target object positioned below said curved mirror, facing toward a front of said image projection system, wherein said target object is selected from the group consisting of a real object, a monitor, a graphic image, a video image, and any object that reflects, transmits, or emits light;

c) a flat fold mirror or reflector positioned below a viewing window of said image projection system, wherein a reflective surface of said flat fold mirror or reflector faces toward said curved mirror and toward said target object, said flat fold mirror or reflector being positioned at an angle such that a target beampath is reflected at a complimentary angle from said target object to said fold mirror to said curved mirror, striking a center or vertex of said curved mirror at an angle equal to twice the angle of tilt of said curved mirror relative to said imaging axis; and

d) a neutral density window or circular polarizer window positioned along said imaging axis of said system, wherein said neutral density filter comprises a neutral density material or a neutral density coating, and wherein light transmitting through said filter is partially absorbed in near equal amounts across the visible light spectrum;

further comprising a primary target beampath or target axis, which represents an imaginary line between a target object to the center of said flat fold mirror or reflector, reflecting off of said fold mirror or reflector at a complimentary angle to an optical center or vertex of a reflective surface of said curved mirror.

2. The real image projection system of claim 1, further comprising an imaging beampath that reflects along a viewing axis of said system, or at a complimentary angle to a target beampath relative to said tilt of said curved mirror, transmitting through a clear reflective substrate, through a window aperture and then forming a real image in space.

3. The real image projection system of claim 1, wherein said curved mirror'"'"'s optical axis is tilted at an angle between 12 degrees and 18 degrees in relationship to an imaging or viewing axis of said system and relative to a target axis as reflected from said fold mirror.

4. The real image projection system of claim 3, wherein said curved mirror comprises:

a) a curved mirror having a spherical surface of revolution;

or

b) a curved mirror having an elliptical surface of evolution, of a configuration whereby said ellipse represents a circle viewed at an angle of incidence equal to said tilt of said curved mirror, thereby reducing distortions at edges of said curved mirror, or

c) a curved mirror having an aspheric surface of revolution for reducing optical aberrations of said system.

5. The real image projection system of claim 1, wherein a real image is positioned along a viewing axis of said system at a focal point of said system, or at a distance equal to twice a focal length of said curved mirror, if said curved mirror is a parabola, or at a distance equal to a radius of a curved sphere, assuming a 1×

magnification, and wherein a target object is located at a distance from said curved mirror equal to a radius of said curved mirror.

6. The real image projection system of claim 5, wherein a position of said target object is other than at a center point of radius for creating a magnified or de-magnified real image.

7. The real image projection system of claim 1, further comprising a background object or monitor or projection screen that is viewed reflected off of a beamsplitter, forming a virtual image located behind a real image, along a viewing axis of said system, and wherein said background object is anything that emits, transmits or reflects light.

8. The real image projection system of claim 1, comprising a curved mirror that has two different surfaces of revolution, one of said two different surfaces of revolution being on a concave surface of said mirror, and another of said two different surfaces of revolution being on a convex surface of said mirror, wherein said real image projection system forms a real image floating in space.

9. The real image projection system of claim 8, comprising an aspheric surface of revolution on said concave surface, and a standard conic or asphere surface of revolution on said convex surface, wherein said convex surface is optically coated with a reflective material.

10. The real image projection system of claim 8, comprising a standard conic or aspheric surface of revolution on said concave surface, and an aspheric surface of revolution on said convex surface, wherein said convex surface is optically coated with a reflective material.

11. The real image projection system of claim 8, further comprising an anti-reflective coating on said concave surface of revolution.

12. The real image projection system of claim 8, comprising a distorted input screen image with pin-cushioning effect, wherein said screen image is distorted in a configuration whereby distortion caused by field curvature distortion is counteracted, thereby causing a video image to distort in a maimer opposite of fisheys effect, thereby producing a true scaled, undistorted real image of an object represented.

13. The real image projection system of claim 1, comprising a distorted input screen image with pin-cushioning effect, wherein said screen image is distorted in a configuration whereby distortion caused by field curvature distortion is counteracted, thereby causing a video image to distort in a manner opposite of fisheye effect, thereby producing a true scaled, undistorted real image of an object presented.

14. A real image projection system, comprising:

a) a curved mirror of elliptical or aspheric surface of revolution, mounted with an optical axis of said mirror at a tilted angle of between 12 and 18 degrees, relative to a target axis of said imaging system from between a target object and a center of said curved mirror, positioned overhead with a front edge of said curved mirror nearest a window aperture positioned lower than a rear edge of said curved mirror;

b) a beamsplitter positioned at a 45 degree angle to an axis of said curved mirror and at an angle equal to 45 degrees plus said tilt angle of said curved mirror relative to said target axis of said imaging system, mounted with a top of said beamsplitter positioned nearest a rear edge of said curved mirror, and a bottom edge of said beamsplitter positioned directly beneath said window viewing aperture;

c) a target object positioned at a point along an optical target axis of said imaging system or along an axis offset by said angle of tilt of said curved minor, with said target axis vertical from said target to a center of said curved mirror, wherein said target object is selected from the group consisting of a real object, a monitor, a graphic image, a video image, and any object that reflects, transmits, or emits light;

d) a window positioned between said beamsplitter and a real image formed by said system, wherein said window is selected from the group consisting of a neutral density substrate, a circular polarizer, or tinted glass; and

e) a real image formed outside said system along said imaging axis.

15. The real image projection system of claim 14, further comprising:

f) a fold mirror or flat reflector positioned along a beampath axis between said target object and said curved mirror, which redirects the beampath, allowing said target object to be repositioned at a point other than along said target axis.

16. The real image projection system of claim 15, further comprising a primary target beampath or target axis, which represents an imaginary line between said target object to a center of said fold mirror, reflecting off of said fold mirror at a complimentary angle to an optical center or vertex of a reflective surface of said curved mirror, striking said curved minor at an angle equal to said tilt of said curved mirror.

17. The real image projection system of claim 14, further comprising an anti-reflective surface applied to one or both surfaces of said window.

18. The real image projection system of claim 14 wherein said curved mirror comprises an elliptical surface of revolution, of which said elliptical curve is an equivalent curvature of a circle viewed at an angle equal to said tilt angle of said curved mirror, so that a lightbeam striking said curved elliptical surface at an offset angle strikes a relative spherical curve.

19. The real image projection system of claim 14, wherein said curved mirror comprises an aspheric surface of revolution, which approximates an elliptical curve and further reduces aberrations of image quality.

20. The real image projection system of claim 14, further comprising an imaging beampath that reflects along said viewing axis or at a complimentary angle to said target beampath, relative to said tilt axis of said curved mirror, away from said viewing aperture, striking a surface of said beamsplitter, reflecting off said beamsplitter surface at a complimentary angle, and transmitting through a window aperture on a horizontal axis plane, and then forming a real image in space.

21. The real image projection system of claim 14, comprising a real image positioned along a viewing axis of said system at a focal point of said system, or at a distance equal to twice a focal length of said curved mirror, if said mirror is a parabola, or at a distance equal to a radius of a curved sphere, assuming a 1×

magnification, and wherein said target object is located at a distance from said mirror equal to a radius of said mirror.

22. The real image projection system of claim 14, wherein a position of said target object is other than at a center point of radius for creating a magnified or de-magnified real image.

23. The real image projection system of claim 14, further comprising a background object that is viewed through said beamsplitter, along a viewing axis of said system, wherein said background object is anything that emits, transmits or reflects light.

24. The real image projection system of claim 14, comprising a distorted input screen image with pin-cushioning effect, wherein said screen image is distorted in a configuration whereby distortion caused by field curvature distortion is counteracted, thereby causing a video image to distort in a manner opposite of fisheye effect, thereby producing a true scaled, undistorted real image of an object represented.