Optical system for a head mounted display using a retro-reflector and method of displaying an image

• US 5,621,572 A
• Filed: 08/24/1994
• Issued: 04/15/1997
• Est. Priority Date: 08/24/1994
• Status: Expired due to Term

• Current Assignee: Fergason Patent Properties
• Original Assignee: James L. Fergason
• Inventors: Fergason, James L.
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/295,383
• Time in Patent Office: 965 Days
• Field of Search: 359/629, 359/630, 359/633, 359/638, 351/211
• US Class Current: 359/630
• CPC Class Codes: G02B 2027/0132 comprising binocular systems
• CPC Class Codes: G02B 2027/0138 comprising image capture systems, e.g. camera
• CPC Class Codes: G02B 2027/0143 the two eyes not being equipped with identical nor symmetrical optical devices
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G03B 15/12 using mirrors

Abstract

A head mounted display system includes focusing optics to focus light from an image source, retro-reflector and beamsplitter, the image source and beamsplitter directing light toward the retro-reflector being directed via the beamsplitter for viewing, thereby to use conjugate optics effectively to place the viewing eye or detector in relation to the image source the same as the relation of the focusing optics or it may be remotely located. A method for forming an image using conjugate optics which light from a source is focused to form a real image at a retro-reflector and is reflected for viewing.

Claims

1. A head mounted display for presenting an image for viewing by a viewer, comprising

a mounting structure mountable on the head of a viewer,

a liquid crystal display image source carried by the mounting structure and providing an image output for viewing by one eye of a viewer,

focusing optics carried by the mounting structure in position to receive light from the image source to form a real image,

a retro-reflector having a characteristic of providing a conjugate optical path leading to said eye of a viewer,

a beamsplitter carried by the mounting structure in position to receive light from the focusing optics and image source and to direct the light toward said retro-reflector, and

said mounting structure including means for holding said beamsplitter and focusing optics with respect to the head of a viewer to orient said focusing optics and said beamsplitter with respect to said eye of the viewer such that said focusing optics and said beamsplitter are in substantially the same relation to each other as the pupil of said eye of a viewer stands in relation to said beamsplitter to permit said eye to view an image from said image source when light representing that image is reflected in said conjugate optical path.

2. The display of claim 1, said mounting structure comprising head gear for mounting on the head of a viewer.

3. The display of claim 2, wherein the size of the display area of the image source is about the size of the image on the retina of said eye of the viewer.

4. The display of claim 1, wherein said retro-reflector is in said conjugate optical path receiving light from said beamsplitter and reflecting light back toward said beamsplitter.

5. The display of claim 4, comprising a further retro-reflector in a further conjugate optical path receiving light from said beamsplitter and reflecting light back to said beamsplitter, said retro-reflector being positioned to reflect in said conjugate optical path light directed to said retro-reflector by reflection from said beamsplitter and said further retro-reflector being positioned to reflect in said further conjugate optical path light directed to said further retro-reflector by transmission through said beamsplitter.

6. The display of claim 1, said focusing optics having an input to receive light from said image source and wherein said image source, said beamsplitter and said focusing optics are cooperatively related effectively to place the lens of the viewer'"'"'s eye at said input to said focusing optics receiving light from said image source.

7. The display of claim 6, said focusing optics having an input to receive light from said image source, and wherein the entrance pupil of the viewer'"'"'s eye forms the exit pupil of the display.

8. The display of claim 1, wherein said retro-reflector is positioned to reflect in said conjugate optical path light directed to said retro-reflector by reflection from said beamsplitter.

9. The display of claim 8, wherein said beamsplitter is positioned relative to the conjugating optical path to direct light received from the retro-reflector toward a viewer for viewing.

10. The display of claim 1, comprising a further image source, said image source and further image source being operative to present to the respective eyes of a viewer respective images.

11. The display of claim 1, comprising a further image source cooperative with said image source to present to the respective eyes of a viewer respective images to form a stereoscopic view.

12. The display of claim 11, further comprising in optical relation to said further image source, a further beamsplitter, and further focusing optics, and

said means for holding including means for holding said further image source, said further beamsplitter and said further focusing optics with respect to the head of a viewer to orient said further focusing optics and said further beamsplitter with respect to the other eye of the viewer such that said further focusing optics and said further beamsplitter are in substantially the same relation to each other as the pupil of such other eye of a viewer stands in relation to said further beamsplitter to view an image from said further image source when light is reflected in a respective conjugate optical path including a portion leading to such other eye.

13. The display of claim 1, comprising a further image source to present an image for viewing by a viewer, said image source and said further image source producing respective images, and said means for holding comprising means for holding each of said image sources in fixed relationship with a respective eye of a viewer to view an image from the respective image source.

14. The display of claim 1, wherein said focusing optics and the eye of a viewer are positionally related to each other along said conjugate optical path in mirror image relation to said beamsplitter.

15. The display of claim 1, wherein said focusing optics and retro-reflector are cooperative to place said image source and retina of the eye of the viewer in conjugate relation.

16. The display of claim 15, wherein the display area of the image source and the size of the area of the image on the retina of the eye of the viewer are about the same size.

17. The display of claim 15, wherein the display area of the image source and the focusing optics are cooperatively related to provide an image on the retina of the eye of the viewer that substantially fills the retina.

18. The display of claim 1, wherein said focusing optics and retro-reflector are cooperative to place said focusing optics and the pupil of the eye of the viewer in conjugate relation.

19. The display of claim 18, wherein the focal length of the focusing optics is substantially the same size as the focal length of the eye.

20. The display of claim 1, wherein said focusing optics comprises means to focus light from the image source to form a real image with respect to the retro-reflector.

21. The display of claim 1, wherein the focusing optics, beamsplitter and conjugate optical path are cooperative to present an image at a viewing location for viewing by the eye of a viewer such that the lens of the eye at the viewing location stands relative to the image source in the same relation as the focusing optics stands relative to the image source.

22. The display of claim 1, wherein said beamsplitter comprises a cholesteric liquid crystal material for reflecting light having one direction of circular polarization and for transmitting light having a different direction of circular polarization.

23. The display of claim 22, further comprising means for providing from the image source circularly polarized light, and wherein said retro-reflector is operative to reverse the direction of circular polarization of circularly polarized light incident thereon, and further comprising means for providing from the image source circularly polarized light, and wherein said retro-reflector is operative to reverse the direction of circular polarization of circularly polarized light incident thereon.

24. The display of claim 1, wherein said image source includes means to provide an image output that has optical polarization characteristic, and said beamsplitter comprises a polarizing beamsplitter cooperative with the polarization characteristic of the image source to reflect light having one polarization characteristic and to transmit light having the opposite polarization characteristic.

25. The display of claim 23, wherein light provided to the retro-reflector is plane polarized for reflection or transmission by the beamsplitter, and further comprising a quarter wave plate in the optical path between the beamsplitter and retro-reflector oriented to convert plane polarized light to circularly polarized light, and wherein said retro-reflector reverses the direction of circular polarization of circularly polarized light incident thereon, whereby upon transmission through the quarter wave plate such reflected light is converted to plane polarized light having a different direction plane of polarization than the light initially provided to the retro-reflector.

26. The display of claim 1, further comprising an optical system that forms a virtual image of light in the conjugate optical path for viewing at the viewing location.

27. The display of claim 26, said optical system comprising a lens.

28. The display of claim 1, said means for holding comprising a housing for at least partly containing said beamsplitter and focusing optics.

29. The display of claim 28, said means for holding comprising means for mounting the image source with respect to the housing.

30. The display of claim 29, said means for holding comprising a support structure supporting the housing in position for relative placement with respect to the head of a viewer to provide respective images to the eyes of the viewer.

31. The display of claim 28, said means for holding further comprising a support for mounting the housing on the head of a viewer.

32. The display of claim 1, wherein said retro-reflector is positioned to reflect in said conjugate optical path light directed to said retro-reflector by transmission through said beamsplitter.

33. A method for viewing an image, comprising

directing light from a liquid crystal display image source for viewing by one eye of a viewer, the image source being mountable with respect to the head of a viewer, said directing including directing light from the liquid crystal display image source via focusing optics and a beamsplitter toward a retro-reflector which has a characteristic of reflecting incident light along a conjugate light path, said directing including forming a real image,

reflecting light by the retro-reflector along such a conjugate light path for viewing by a viewer, and

positioning the pupil of the eye of a viewer to stand in the same relation to the beamsplitter as the focusing optics stands in relation to the beamsplitter to view an image from the image source when light is reflected in the conjugate light path.

34. The method of claim 33, said directing including directing light from the focusing optics via the beamsplitter to the retro-reflector and said reflecting light comprising directing light reflected by the retro-reflector via the beamsplitter to the eye for viewing.

35. The method of claim 33, said directing comprising presenting such image for viewing by one eye of a viewer and presenting an image to the other eye of the viewer, including directing light from a further image source via focusing optics in a further conjugate optical path in which the further image source and the other eye of the viewer are in conjugate relationship to view an image from the further image source when light is reflected in the further conjugate optical path.

36. The method of claim 33, said directing comprising presenting such image for viewing by one eye of a viewer and presenting an image to the other eye of the viewer to provide stereoscopic view, including directing light from a further image source via focusing optics in a further conjugate optical path in which the further image source and the other eye of the viewer are in conjugate relationship to view an image from the further image source when light is reflected in the further conjugate optical path.

37. The method of claim 33, said positioning comprising mounting the focusing optics and beamsplitter with respect to the head of the viewer.

38. The method of claim 37, said positioning comprising mounting the focusing optics and beamsplitter on the head of the viewer as a head mounted display.

39. The method of claim 33, said positioning comprising mounting the focusing optics, beamsplitter and image source with respect to a housing having a viewing outlet at which a viewer may view an image.

40. A method for viewing an image, comprising

directing light from liquid crystal display image source for viewing by one eye of a viewer, the image source being mountable with respect to the head of a viewer, said directing including directing the light from the liquid crystal display image source via focusing optics and a beamsplitter to form a real image, the focusing optics and beamsplitter being positioned in relation to each other and said directing light comprising directing light along a conjugate light path,

reflecting light along the conjugate light path via the beamsplitter to the eye of a viewer,

said directing light via focusing optics comprising directing light via focusing optics which has a focal length about the same or smaller than the focal length of the eye of the viewer, and

positioning the focusing optics and beamsplitter relative to the viewer such that the pupil of the eye stands in the same relation to the beamsplitter as the focusing optics stands in relation to the beamsplitter to view an image from the image source when light is reflected in the conjugate light path.