Near-eye image projection system having foveated projection and expanded eye-box region
A near-eye image projection system, comprising a pin-light array generating incident light beams illuminating an optical light modulator configured for modulating the incident light beams and projecting modulated light-beams; an optical element configured to project the modulated light beams such as to form pin-light images and project projected image light beams defining an eye-box region along a projection axis. The modulated light beams comprise foveal modulated light beams forming foveal pupil images and projecting foveal projected image light beams defining a foveal eye-box region, and peripheral modulated light beams forming peripheral pupil images. An exit pupil expansion device is configured to project pupil expanded light beams for each of the peripheral pin-light images and to form peripheral projected image light beams defining a peripheral eye-box region wider than the foveal eye-box region.
1 . A near-eye image projection system, comprising:
a pin-light array generating a plurality of incident light beams illuminating an optical light modulator configured for modulating the incident light beams and projecting a plurality of modulated light-beams;
an optical element configured to project the plurality of modulated light beams such as to form pin-light images at a first pin-light plane and project a plurality of projected image light beams defining an eye-box region along a projection axis;
wherein said plurality of modulated light beams comprises a plurality of foveal modulated light beams forming foveal pupil images and projecting a plurality of foveal projected image light beams defining a foveal eye-box region;
wherein said plurality of modulated light beams further comprises a plurality of peripheral modulated light fields forming peripheral pupil images;
the system further comprising an exit pupil expansion device configured to project a plurality of pupil expanded light beams for each of the peripheral pin-light images, said plurality of pupil expanded light beams forming peripheral projected image light beams defining a peripheral eye-box region wider than the foveal eye-box region;
wherein the expansion device is configured to transmit the foveal modulated light beams unaffected by the expansion device, such that the foveal modulated light beams form foveal modulator images at a modulator image plane;
wherein the optical element comprises a first pin-light image optical element configured to project the plurality of foveal modulated light beams such as to form foveal modulator images at the modulator image plane; and
wherein the image projection system further comprises, at the first pin-light plane, a deflecting element configured to deflect said peripheral modulated light beams with respect to the projection axis and form shifted modulator images spatially shifted along the modulator image plane.
2 . The image projection system according to claim 1 , wherein the exit pupil expansion device further comprises a diffuser element at the modulator image plane.
3 . The image projection system according to claim 1 , wherein the expansion device comprises a waveguide extending in the first pin-light plane, the waveguide comprising an in-coupling element configured to input said peripheral pin-light image, and an out-coupling element configured to project said plurality of pupil expanded light beams.
4 . The image projection system according to claim 3 , wherein the out-coupling element is configured to project a plurality of discrete pupil expanded light beams.
5 . The image projection system according to claim 3 , wherein the out-coupling element is configured to project continuously distributed pupil expanded light beams.
6 . The image projection system according to claim 3 , further comprising a beam focusing element configured to focus the plurality of pupil expanded light beams such as to form the shifted modulator images.
7 . The image projection system according to claim 6 , wherein the in-coupling element is configured to collimate the peripheral modulated light beams.
8 . The image projection system according to claim 3 , wherein at least one of the in-coupling element or out-coupling element comprises a holographic optical element.
9 . The image projection system according to claim 3 , wherein at least one of the in-coupling element or out-coupling element comprises a mirror array or a stack of partly transparent mirrors.
10 . The image projection system according to claim 3 , wherein at least one of the in-coupling element or out-coupling element comprises a diffraction grating.
11 . The image projection system according to claim 3 , wherein the aperture openings are provided in the waveguide, each aperture opening being configured to transmit the pin-light image.
12 . The image projection system according to claim 1 , wherein the deflecting element comprises a prism.
13 . The image projection system according to claim 1 , comprising a second optical element configured to interact with the plurality of modulated light beams such as to project a plurality of projected image light beams defining an eye-box region along a projection axis.
14 . The image projection system according to claim 13 , wherein the second optical element comprises a combiner configured to transmit natural light from the real world towards the eye-box region.
15 . The image projection system according to claim 1 wherein the exit pupil expansion element comprises an off-axis optics and a diffuser element, the off-axis optics being configured to project the peripheral modulated light beams on the diffuser element, the diffuser element projecting the pupil expanded light beams along the projection axis, substantially orthogonal to an incident projection axis parallel to the foveal and peripheral incident light-beam; and
wherein the image projection system comprises a beam splitter reflecting the foveal modulated light beams along the projection axis, the reflected foveal modulated light beams being combined to the pupil expanded light beams in the optical element.
16 . The image projection system according to claim 1 wherein the exit pupil expansion element comprises a light-guide configured to guide a peripheral modulated light beam and projects the pupil expanded light beams from an out-coupling element provided in the light-guide along the projection axis making an angle relative to an incident projection axis parallel to the foveal and peripheral incident light-beam; and
wherein the foveal modulated light beams are reflected on the second optical element along the projection axis.
17 . The image projection system according to claim 1 , comprising an eye-tracking and steering device configured to provide eye-tracking information about where a viewer is looking; and
wherein the eye-tracking and steering device is configured to deflect the peripheral projected image light beams in accordance to eye-tracking information.
18 . The image projection system according to claim 17 ,
wherein the eye-tracking and steering device comprises a mirror or lens movable in accordance to eye-tracking information.
19 . The image projection system according to claim 18 ,
wherein the eye-tracking and steering device is configured to provide non-light-field images outside the first eye-box region when the eye-tracking information indicates that the viewer is looking outside the first eye-box region.