Holographic Waveguide Optics for Virtual Surface Artefact Separation
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Solution Overview
Problem
Existing holographic projectors suffer from visual artefacts on a virtual surface formed by waveguide replicas, which distract viewers and reduce the quality of the holographic reconstruction experience.
Innovation Solution
An optical system is designed with an optical component that forms a virtual image of the holographic reconstruction far removed from the image of the hologram, minimizing the impact of these artefacts by positioning the hologram/image of the display device at infinity or downstream of the viewing system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If waveguide pupil expanders are used to expand the exit pupil of the optical system, then the viewing window and field of view are increased, but visual artefacts are formed on the virtual surface which distract viewers and reduce image quality
Solution Approach 1:
The patent extracts and removes the harmful virtual surface artefacts from the optical path by positioning the display device image at infinity or downstream of the viewing system, separating it from the virtual image location where artefacts would otherwise be visible to viewers
Solution Approach 2:
The patent introduces an intermediary optical component (such as a lens or optical relay) that mediates between the waveguide pupil expanders and the virtual image formation, allowing the viewing window to be expanded while preventing artefacts from reaching the viewer's eye
2Device complexity
If the image of the hologram is positioned close to the virtual image of the holographic reconstruction, then the optical system is more compact, but artefacts on the virtual surface distract viewers from the holographic reconstruction
Solution Approach 1:
The patent resolves the contradiction by moving the display device image to a different depth dimension (at infinity or downstream of the viewing system) rather than keeping it in the same plane as the virtual image, allowing compact lateral arrangement while maintaining large longitudinal separation to eliminate artefact visibility
3Illumination intensity
If the exit pupil is expanded using waveguides, then more light reaches the viewer and image brightness is improved, but repeating patterns of artefacts are formed that draw viewer attention
Solution Approach 1:
The patent extracts the harmful repeating artefact patterns from the optical path by positioning the display device image outside the virtual image depth, removing the source of artefacts that would otherwise be superimposed on the bright holographic reconstruction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces the distraction caused by virtual surface artefacts, enhancing the viewing experience by allowing viewers to focus on the holographic reconstruction without being drawn to repeating patterns of artefacts.
Implementation Method 1
The display device may be positioned at a front focal plane of the first lens. The optical system may be arranged such that the display device is illuminated with coherent light which is spatially modulated in accordance with the hologram and then received by the first lens of the optical relay such that a holographic reconstruction of the picture is formed at the back focal plane of the first lens.
Implementation Method 2
The light may then continue to propagate and be received by the second lens of the optical relay such that a relayed image of the display device (i.e. a relayed image of the hologram) may be formed at the back focal plane of the second lens.
Implementation Method 3
A first waveguide is positioned near the back focal plane of the second lens and may be arranged to receive the spatially modulated light and replicate that light to expand an exit pupil of the optical system in a first direction. A second waveguide may also be provided arranged to receive the light output from the first waveguide to expand the exit pupil of the optical system in a second direction.
Data Source
AI summary
There is provided an optical system having a viewing window. The optical system comprises a display device arranged to spatially modulated light in accordance with a hologram displayed thereon to form a holographic wavefront. The holographic wavefront forms a holographic reconstruction of an image downstream of the display device. The optical system further comprises a waveguide arranged to receive the holographic wavefront and waveguide the holographic wavefront between a pair of reflective surfaces thereof. One surface of the pair of reflective surfaces is partially transmissive such that a plurality of replicas of the holographic wavefront are emitted therefrom. The optical system further comprises an optical component between the holographic reconstruction and the waveguide, wherein the optical component is arranged to (a) form a virtual image of the holographic reconstruction upstream of the display device and (b) form an image of the displayed hologram at infinity or downstream of the waveguide.