Aperture multiplier using a rectangular waveguide

• US 10,133,070 B2
• Filed: 09/12/2017
• Issued: 11/20/2018
• Est. Priority Date: 10/09/2016
• Status: Active Grant

• Current Assignee: Lumus Ltd.
• Original Assignee: Lumus Ltd.
• Inventors: Danziger, Yochay
• Primary Examiner(s): Beatty, Collin X
• Application Number:
  US15/749,511
• Publication Number:
  US 20180210202A1
• Time in Patent Office: 434 Days
• Field of Search: 359630, 359 15, 359629, 359633, 359 34, 359618, 359857, 359471, 345 7, 385 24, 385 31, 385 50, 362346
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• CPC Class Codes: G02B 6/2786 Reducing the polarisation degree, i.e. depolarisers, scramblers, unpolarised output
• CPC Class Codes: G02F 1/295 Analog deflection from or in an optical waveguide structure]
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor

Abstract

An optical aperture multiplier includes a first optical waveguide (10) having a rectangular cross-section and including partially reflecting surfaces (40) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide (20), also including partially reflecting surfaces (45) at an oblique angle, is optically coupled with the first optical waveguide (10). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.

Claims

1. An optical aperture multiplier comprising:

(a) a first optical waveguide having a direction of elongation, said first optical waveguide having first and second pairs of parallel faces forming a rectangular cross-section, wherein a plurality of partially reflecting surfaces at least partially traverse said first optical waveguide, said partially reflecting surfaces being at an oblique angle to said direction of elongation; and

(b) a second optical waveguide optically coupled with said first optical waveguide, said second optical waveguide having a third pair of parallel faces forming a slab-type waveguide, wherein a plurality of partially reflecting surfaces at least partially traverse said second optical waveguide, said partially reflecting surfaces being at an oblique angle to said third pair of parallel faces,

wherein said optical coupling and said partially reflecting surfaces of said first and second waveguides are configured such that, when an image is coupled into said first optical waveguide with an initial direction of propagation at a coupling angle oblique to both said first and second pairs of parallel faces, the image advances by four-fold internal reflection along said first optical waveguide, with a proportion of intensity of the image reflected at said partially reflecting surfaces so as to be coupled into said second optical waveguide, and propagating through two-fold reflection within said second optical waveguide, with a proportion of intensity of the image reflected at said partially reflecting surfaces so as to be directed outwards from one of said parallel faces as a visible image.

2. The optical aperture multiplier of claim 1, wherein said first pair of parallel faces comprises a first face and a second face, and said second pair of parallel faces comprises a third face and a fourth face, an end of said first face terminating at a first proximal edge and an end of said third face terminating at a second proximal edge,

the optical aperture multiplier further comprising a coupling reflector arrangement integrally formed, or optically coupled, with said optical waveguide, said coupling reflector arrangement comprising:

(a) a first reflector deployed as a proximal extension of said third face, or as a reflector parallel and external to said third face, said first reflector having a width perpendicular to said direction of elongation that is greater than a width of said third surface, and

(b) a second reflector deployed as a proximal extension of said fourth face, or as a reflector parallel and external to said fourth face, said second reflector having a width perpendicular to said direction of elongation that is greater than a width of said fourth surface,

such that, when viewed along an optical input axis, said first and second proximal edges present an apparent waveguide aperture bounded by said first and second proximal edges and images of said first and second proximal edges reflected in said coupling reflector arrangement.

3. The optical aperture multiplier of claim 2, wherein said optical input axis is oblique to both said first and second reflectors.

4. The optical aperture multiplier of claim 2, wherein said coupling reflector arrangement is implemented as a coupling prism integrally formed, or optically coupled, with said optical waveguide, said coupling prism presenting a coupling surface generally perpendicular to the optical input axis.

5. The optical aperture multiplier of claim 2, wherein said coupling reflector arrangement is implemented as a coupling prism integrally formed, or optically coupled, with said optical waveguide, said coupling prism being integrated with at least one optical element of an image projection arrangement.

6. The optical aperture multiplier of claim 5, wherein said at least one optical element comprises a beam splitter prism having an input face, a reflector face, an internal inclined beam-splitting element and an output face generally orthogonal to a primary direction of output image propagation, and wherein at least part of said first and second reflectors of said coupling reflector extend across a plane of said output face.

7. The optical aperture multiplier of claim 2, wherein said coupling reflector arrangement is implemented as a coupling prism integrally formed, or optically coupled, with said optical waveguide, said coupling prism presenting an oblique reflecting surface for reflecting light input along an optical axis perpendicular to one of said first and second reflectors so as to impinge on said apparent waveguide aperture.

8. The optical aperture multiplier of claim 2, further comprising an image projector deployed to project an image collimated to infinity along the optical input axis so as to fully overlap said apparent waveguide aperture.

9. The optical aperture multiplier of claim 8, further comprising a depolarizer element interposed in an optical path between said image projector and said coupling reflector arrangement.

10. The optical aperture multiplier of claim 1, wherein said first optical waveguide is optically coupled to an end surface of said second optical waveguide, said end surface extending between said third pair of parallel faces.

11. The optical aperture multiplier of claim 10, wherein said end surface is orthogonal to said third pair of parallel faces.

12. The optical aperture multiplier of claim 10, wherein said end surface is angled obliquely to said third pair of parallel faces.

13. The optical aperture multiplier of claim 10, wherein said partially reflective surfaces of said second waveguide intersect a first of said third pair of parallel faces at a set of parallel lines, and wherein said end surface meets said first of said third pair of parallel faces along an edge, said edge being non-parallel to said set of parallel lines.

14. The optical aperture multiplier of claim 1, wherein said first optical waveguide is optically coupled to one of said third pair of parallel faces.

15. The optical aperture multiplier of claim 1, wherein said partially reflecting surfaces of said first waveguide are at an oblique angle to both said first pair of parallel faces and said second pair of parallel faces.

16. The optical aperture multiplier of claim 1, wherein at least one face from said first and second pairs of parallel faces is coated with layers of a dielectric material to form a dielectric mirror.

17. The optical aperture multiplier of claim 1, wherein one of said faces of said first optical waveguide is a coupling face through which said first optical waveguide is optically coupled with said second optical waveguide, and wherein said plurality of partially reflecting surfaces of said first waveguide are in overlapping relation such that, in a geometrical projection of said partially reflecting surfaces along a primary image propagation direction onto said coupling face, a majority of an area lying within the projection is included within projections of at least two of said partially reflecting surfaces.

18. The optical aperture multiplier of claim 1, further comprising an image projecting arrangement associated with said first waveguide and deployed to introduce into said first waveguide a first image with a first spread of angular directions, and wherein said four-fold internal reflection generates second, third and fourth conjugate images having respective second, third and fourth spreads of angular directions,

said plurality of partially reflecting surfaces of said first optical waveguide being coated so as to render them substantially transparent to rays of said image incident within a first range of angles to said partially reflecting surfaces and partially reflecting to rays of said image incident within a second range of angles,

wherein said first spread of angular directions and the oblique angle of said plurality of partially reflecting surfaces are chosen such that said spread of angular directions for three of said four conjugate images are all incident on said plurality of partially reflecting surfaces within said first range of angles and said spread of angular directions for only one of said four conjugate images is incident on said plurality of partially reflecting surfaces within said second range of angles.

19. An optical aperture multiplier comprising:

(a) an optical waveguide having a direction of elongation, said optical waveguide having a first pair of parallel faces comprising a first face and a second face, and a second pair of parallel faces comprising a third face and a fourth face, said pairs of parallel faces together forming a rectangular cross-section, an end of said first face terminating at a first proximal edge and an end of said third face terminating at a second proximal edge; and

(b) a coupling reflector arrangement integrally formed, or optically coupled, with said optical waveguide, said coupling reflector arrangement comprising;

(i) a first reflector deployed as a proximal extension of said third face, or as a reflector parallel and external to said third face, said first reflector having a width perpendicular to said direction of elongation that is greater than a width of said third surface, and

(ii) a second reflector deployed as a proximal extension of said fourth face, or as a reflector parallel and external to said fourth face, said second reflector having a width perpendicular to said direction of elongation that is greater than a width of said fourth surface,

such that, when viewed along an optical input axis, said first and second proximal edges present an apparent waveguide aperture bounded by said first and second proximal edges and images of said first and second proximal edges reflected in said coupling reflector arrangement.

20. The optical aperture multiplier of claim 19, wherein said optical input axis is oblique to both said first and second reflectors.

21. The optical aperture multiplier of claim 19, wherein said coupling reflector arrangement is implemented as a coupling prism integrally formed, or optically coupled, with said optical waveguide, said coupling prism presenting a coupling surface generally perpendicular to the optical input axis.

22. The optical aperture multiplier of claim 19, further comprising an image projector deployed to project an image collimated to infinity along the optical input axis so as to fully overlap said apparent waveguide aperture.

23. The optical aperture multiplier of claim 22, further comprising a depolarizer element interposed in an optical path between said image projector and said coupling reflector arrangement.

24. An optical aperture multiplier comprising:

(a) a first optical waveguide having a direction of elongation, said first optical waveguide having first and second pairs of parallel faces forming a rectangular cross-section, wherein a plurality of partially reflecting surfaces at least partially traverse said first optical waveguide, said partially reflecting surfaces being at an oblique angle to said direction of elongation, said plurality of partially reflecting surfaces of said first optical waveguide being coated so as to render them substantially transparent to rays incident within a first range of angles to said partially reflecting surfaces and partially reflecting to rays incident within a second range of angles; and

(b) an image projecting arrangement associated with said first waveguide and deployed to introduce into said first waveguide a first image with a first spread of angular directions,

wherein said first image advances by four-fold internal reflection along said first optical waveguide, thereby generating second, third and fourth conjugate images having respective second, third and fourth spreads of angular directions,

and wherein said first spread of angular directions and the oblique angle of said plurality of partially reflecting surfaces are chosen such that said spread of angular directions for three of said four conjugate images are all incident on said plurality of partially reflecting surfaces within said first range of angles and said spread of angular directions for only one of said four conjugate images is incident on said plurality of partially reflecting surfaces within said second range of angles.