Optical device and virtual image display device

• US 7,747,113 B2
• Filed: 06/06/2008
• Issued: 06/29/2010
• Est. Priority Date: 03/29/2004
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Akutsu, Katsuyuki, Mukawa, Hiroshi
• Primary Examiner(s): Healy; Brian M.
• Assistant Examiner(s): Anderson; Guy G
• Application Number:
  US12/134,846
• Publication Number:
  US 20080239424A1
• Time in Patent Office: 753 Days
• Field of Search: 359 15- 17, 359/71, 235/462, 385/31
• US Class Current: 385/31
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 17/004 Systems comprising a plurality of reflections between two or more surfaces, e.g. cells, resonators multipass arrangements for optical cuvettes G01N21/031; laser resonators H01S3/05
• CPC Class Codes: G02B 17/006 Systems in which light light is reflected on a plurality of parallel surfaces, e.g. louvre mirrors, total internal reflection [TIR] lenses Fresnel mirrors G02B5/09, Fresnel lenses G02B3/08
• 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 2027/0116 comprising devices for correcting chromatic aberration
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/005 : provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/2848 : having refractive means, e.g. imaging elements between light guides as splitting, branching and/or combining devices, e.g. lenses, holograms
• CPC Class Codes: G02B 6/43 : Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections

Abstract

A virtual image display device is provided which displays a two-dimensional image for viewing a virtual image in a magnified form by a virtual optical system. The virtual image display device includes an optical waveguide (13) to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating (14) to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating (15) to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide. Some of the parallel pencil groups guided through the optical waveguide being totally reflected different numbers of times for a period from external incidence upon the optical waveguide until outgoing from the optical waveguide.

Claims

1. A virtual image display device comprising:

a light source to emit a pencil of rays;

a collimating optical system to form the pencil from the light source into a parallel pencil;

a scanning optical system to form, by horizontal and vertical scan, the parallel pencil into parallel pencil groups traveling in different directions;

an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection inside the optical waveguide;

a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from the scanning optical system and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide; and

a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide,

wherein,

some parallel pencils of the parallel pencil groups guided through the optical waveguide being totally reflected a different number of times for a period from external incidence upon the optical waveguide until outgoing from the optical waveguide,

the second reflection volume hologram grating reflects and diffracts some parallel pencils of the incident parallel pencil groups a plurality of times to project the parallel pencils from the optical waveguide at each diffraction and reflection, and

the interference fringe recorded on the first reflection volume hologram grating is equal in pitch on the hologram surface to that recorded on the second reflection volume hologram grating such that parallel rays of light incident at a same wavelength and incident angle are diffracted and reflected at a same angle.

2. The virtual image display device according to claim 1, wherein the first and second reflection volume hologram gratings are disposed with their hologram planes being parallel to a total reflection surface at which the parallel pencil groups are totally reflected inside the optical waveguide.

3. The virtual image display device according to claim 1, wherein:

the first and second reflection volume hologram gratings have recorded thereon a plurality of interference fringes having a predetermined slant angle and identical to each other; and

the first and second reflection volume hologram gratings are disposed with the plurality of interference fringes recorded thereon being symmetrical with each other with respect to a predetermined plane of symmetry.

4. The virtual image display device according to claim 1, wherein:

the first reflection volume hologram grating is formed from a lamination of a plurality of hologram layers having recorded thereon interference fringes different from each other, each of the hologram layers diffracting and reflecting the parallel pencil groups incident at the same angle and different in waveband from each other at a nearly same angle of diffraction and reflection; and

the second reflection volume hologram grating is formed from a lamination of a plurality of hologram layers having recorded thereon interference fringes different from each other, each of the hologram layers diffracting and reflecting the parallel pencil groups incident at the same angle and different in waveband from each other at a nearly same angle of diffraction and reflection.

5. The virtual image display device according to claim 4, wherein each of the first and second reflection volume hologram gratings has recorded thereon at least a set of interference fringes equal in interference fringe pitch on the hologram surface to each other to diffract and reflect the parallel pencil groups nearly equal in waveband to each other.

6. The virtual image display device according to claim 1, wherein:

the first reflection volume hologram grating has recorded thereon a group of interference fringes formed from a combination of a plurality of interference fringes different from each other, the first reflection volume hologram grating diffracting and reflecting the parallel pencil groups incident at the same angle and different in waveband from each other at a nearly same angle of reflection; and

the second reflection volume hologram grating has recorded thereon a group of interference fringes formed from a combination of a plurality of interference fringes different from each other, the second reflection volume hologram grating diffracting and reflecting the parallel pencil groups incident at the same angle and different in waveband from each other at a nearly same angle of reflection.

7. The virtual image display device according to claim 6, wherein each of the first and second reflection volume hologram gratings has recorded thereon at least a set of interference fringes equal in interference fringe pitch on the hologram surface to each other to diffract and reflect the parallel pencil groups nearly equal in waveband to each other.

8. The virtual image display device according to claim 1, wherein:

the first reflection volume hologram grating is formed from a lamination of a plurality of hologram layers having recorded thereon interference fringes different from each other, each of the hologram layers diffracting and reflecting the parallel pencil groups nearly equal in waveband to each other with different efficiencies of diffraction correspondingly to the incident angle of the parallel pencil groups and diffracting and reflecting the parallel pencil groups incident at the same angle and nearly equal in waveband to each other at the same angle of diffraction; and

the second reflection volume hologram grating is formed from a lamination of a plurality of hologram layers having recorded thereon interference fringes different from each other, each of the hologram layers diffracting and reflecting the parallel pencil groups nearly equal in waveband to each other with different efficiencies of diffraction correspondingly to the incident angle of the parallel pencil groups and diffracting and reflecting the parallel pencil groups incident at the same angle and nearly equal in waveband to each other at the same angle of diffraction.

9. The virtual image display device according to claim 8, wherein each of the first and second reflection volume hologram gratings has recorded thereon at least a set of interference fringes equal in interference fringe pitch on the hologram surface to each other to diffract and reflect the parallel pencil groups nearly equal in waveband to each other.

10. The virtual image display device according to claim 1, wherein:

the first reflection volume hologram grating has recorded thereon a group of interference fringes formed from a combination of a plurality of interference fringes different from each other, the first reflection volume hologram grating diffracting and reflecting the parallel pencil groups nearly equal in waveband to each other with different efficiencies of diffraction correspondingly to the incident angle of the parallel pencil groups and diffracting and reflecting the parallel pencil groups incident at the same angle and nearly equal in waveband to each other at the same angle of diffraction; and

the second reflection volume hologram grating has recorded thereon a group of interference fringes formed from a combination of a plurality of interference fringes different from each other, the second reflection volume hologram grating diffracting and reflecting the parallel pencil groups nearly equal in waveband to each other with different efficiencies of diffraction correspondingly to the incident angle of the parallel pencil groups and diffracting and reflecting the parallel pencil groups incident at the same angle and nearly equal in waveband to each other at the same angle of diffraction.

11. The virtual image display device according to claim 10, wherein each of the first and second reflection volume hologram gratings has recorded thereon at least a set of interference fringes equal in interference fringe pitch on the hologram surface to each other to diffract and reflect the parallel pencil groups nearly equal in waveband to each other.

14. The virtual image display device according to claim 1, wherein:

the optical waveguide is formed with at least a hologram layer inserted between any two of a plurality of laminated transparent substrates; and

the hologram layer has the first and reflection volume hologram gratings formed thereon.

15. The virtual image display device according to claim 14, wherein an area of the hologram layer where the first and second reflection volume hologram gratings are not formed is taken as an airspace.

16. The virtual image display device according to claim 1, wherein:

the light source includes a red light-emitting light source, green light-emitting light source and a blue light-emitting light source; and

there is also provided a color synthesizing means to make color synthesis of the red light, green light and blue light.

17. The virtual image display device according to claim 1, where in the scanning optical system includes at least a moving mirror freely movable in a two-dimensional direction.

18. The virtual image display device according to claim 1 wherein the scanning optical system includes at least two moving mirrors movable in one-dimensional directions, respectively, perpendicular to each other.

19. The virtual image display device according to claim 1, wherein the first reflection volume hologram grating and the second reflection volume hologram grating do not act as a lens thereby eliminating monochromatic eccentric aberration and reducing diffraction chromatic aberration.

12. A virtual image display device comprising:

a light source to emit a pencil of rays;

a collimating optical system to form the pencil from the light source into a parallel pencil;

a scanning optical system to form, by horizontal and vertical scan, the parallel pencil into parallel pencil groups traveling in different directions;

an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection inside the optical waveguide;

a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from the scanning optical system and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide; and

a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide,

wherein,

some parallel pencils of the parallel pencil groups guided through the optical waveguide being totally reflected a different number of times for a period from external incidence upon the optical waveguide until outgoing from the optical waveguide,

the second reflection volume hologram grating reflects and diffracts some parallel pencils of the incident parallel pencil groups a plurality of times to project the parallel pencils from the optical waveguide at each diffraction and reflections,

the second reflecting volume hologram grating has, near the first reflection volume hologram grating, a first area having recorded therein a plurality of interference fringes having a second slant angle smaller than a first slant angle that is a slant angle of an interference fringe for a maximum diffraction efficiency of the parallel pencil groups diffracted and reflected perpendicularly to the second reflection volume hologram grating in order to diffract the incident parallel pencil groups with a maximum efficiency, and

the second reflecting volume hologram grating has, far from the first reflection volume hologram grating, a second area having recorded therein a plurality of interference fringes having a third slant angle larger than the first slant angle in order to diffract the incident parallel pencil groups with a maximum efficiency.

13. The virtual image display device according to claim 12, wherein the second reflection volume hologram grating has located at the center thereof a third area having recorded therein at least one interference fringe having the second slant angle and also at least one interference fringe having the third slant angle.