Light guide optical assembly
An optical assembly for optical aperture expansion combines facet reflective technology with diffractive technology. At least two diffractive components having opposite optical power (matching) are used, so that chromatic dispersion introduced by the first diffractive component will then be cancelled by the second diffractive component. The two diffractive components are used in combination with a reflective optical component to achieve more efficient aperture expansion (for near eye display), reducing distortions and noise, while also reducing design constraints on the system and individual components, as compared to conventional techniques. The assembly eliminates and/or reduces the need for polarization management, while enabling wider field of view. In addition, embodiments can have reduced nonuniformity, as compared to conventional single technology implementations, since the distortion patterns of the two technologies do not correlate.
1. An optical system that redirects light produced by a display module towards an eye of an observer, the optical system comprising:
a waveguide having a pair of mutually-parallel major surfaces;
a non-diffractive input coupler configured to directly couple the light produced by the display module into the waveguide so as to propagate within the waveguide in an input direction by internal reflection at the major surfaces;
a diffractive arrangement integrated with the waveguide configured to diffract the light propagating within the waveguide in the input direction through a first diffraction that redirects the light so as to propagate within the waveguide in a first direction non-parallel to the input direction by internal reflection at the major surfaces, and through a second diffraction which progressively redirects the light propagating within the waveguide in the first direction so as to propagate within the waveguide by internal reflection at the major surfaces in a second direction parallel to the input direction while expanding the light in the first direction; and
an output coupler comprising a plurality of partially-reflecting surfaces angled obliquely to the major surfaces of the waveguide, the output coupler progressively coupling the light expanded in the first direction by the diffractive arrangement out of the waveguide towards the eye of the observer while expanding the light in the second direction.
2. The optical system of claim 1 , wherein said diffractive arrangement comprises a first diffractive optical component and a second diffractive optical component.
3. The optical system of claim 2 , wherein said first diffractive optical component is a strongly diffracting component, and wherein said second diffractive optical component is configured to progressively diffract the light while expanding the light in the first direction.
4. The optical system of claim 2 , wherein said first diffractive optical component and said second diffractive optical component have matching optical power such that a second of said diffractions cancels a chromatic dispersion introduced by a first of said diffractions.
5. The optical system of claim 1 , wherein said diffractive arrangement is configured such that a second of said diffractions cancels a chromatic dispersion introduced by a first of said diffractions.
6. The optical system of claim 1 , wherein said diffractive arrangement includes at least one grating on a surface of said waveguide.
7. The optical system of claim 1 , wherein said diffractive arrangement includes at least one diffractive grating embedded in said waveguide.
8. The optical system of claim 1 , wherein said diffractive arrangement includes at least one holographic element.