Lightguide-based display with light recirculation
AssigneeLumus Ltd.
InventorsElad SHARLIN, Ronen CHRIKI
Life of this patent
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Abstract
A display includes a lightguide arrangement in which at least part of the image light is not coupled-out from the lightguide during a first pass of a coupling-out arrangement, and is recirculated so as to pass repeatedly the coupling-out arrangement. In one set of embodiments, recirculation of light is performed via a separate lightguide. In another set of embodiments, light is recirculated within a single lightguide, employing polarization management to avoid unwanted interactions between the light and the coupling-out arrangement.
Claims5
A display for delivering image light to an observer, the display comprising:
- a) a lightguide comprising a block of transparent material having mutually parallel first and second major surfaces for supporting propagation of image light by internal reflection at the first and second major surfaces;
- b) a set of internal mutually parallel partially reflecting surfaces obliquely angled to the major surfaces and oriented to couple out part of the image light propagating within the lightguide in a first direction so as to be reflected towards an observer while transmitting part of the image light to continue propagating in the first direction within the lightguide;
- c) a first planar mirror associated with a first edge of the lightguide and deployed to reflect the image light transmitted by the set of partially reflecting surfaces so as to propagate within the lightguide in a second direction back towards the partially reflecting surfaces;
- and
- d) a second planar mirror associated with a second edge of the lightguide and deployed to reflect the image light returned through the partially reflecting surfaces so as to propagate within the lightguide in the first direction,
- wherein the partially reflecting surfaces have angularly selective reflecting properties so as to be partially reflective within a first range of incident angles and to be substantially transparent within a second range of incident angles,
- and wherein image light propagating in the first direction that, after internal reflection at the first major surface, is incident on the partially reflecting surfaces within the first range of angles is incident, after internal reflection at the second major surface, within the second range of angles,
- and wherein the first planar mirror and the second planar mirror are obliquely angled to the first major surface such that, after reflection of the image light by the first planar mirror, the image light propagating in the second direction is incident on the partially reflecting surfaces within the second range of incident angles both after reflection in the first major surface and after reflection in the second major surface,
- such that at least part of the image light transmitted by the set of partially reflecting surfaces, reflected at the first planar mirror, transmitted again by the set of partially reflecting surfaces and reflected at the second planar mirror, is incident on the partially reflecting surfaces within the first range of incident angles so as to be partially reflected and coupled out towards the observer.
The display of claim, further comprising an image injection aperture for injecting the image light into the lightguide so as to propagate in the first direction by internal reflection at the major surfaces, and wherein the first direction is inclined relative to a direction of elongation of the first and second planar mirrors such that the image light introduced at the image injection aperture is incident on a first region of the partially reflecting surfaces and, after reflection from the first reflective configuration and the second reflective configuration, is incident on a second region of the partially reflecting surfaces, the second region being at least partially non-overlapping with the first region.
The display of claim, wherein a reflectivity of the partially-reflecting surfaces in at least the first region within the first range of incident angles is such that a majority of the image light injected at the image injection aperture is transmitted through the set of partially reflecting surfaces and recirculated by reflection at the first and second reflective configurations.
The display of claim, further comprising a partially reflecting surface deployed internally to the lightguide, perpendicular to the major surfaces and parallel to a direction of elongation of the first and second planar mirrors.
Dependencies are inferred from the claim text.