Polarization-Sensitive Grating for Near-Eye Display Rainbow Removal
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Solution Overview
Problem
Near-eye display systems using diffractive optical elements are susceptible to rainbows caused by external real-world and stray light, which can compromise display effectiveness by mixing with virtual images and reducing image clarity.
Innovation Solution
A polarizing filter is used at the front of the system to ensure incoming real-world/stray light is TM-polarized, while a downstream out-coupling DOE with diffractive grating structures is configured to be sensitive only to TE-polarized light, allowing only virtual-world objects to be diffracted for display, thereby preventing rainbows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If diffractive optical elements are used to control light shape in near-eye display, then light control flexibility is improved, but rainbow phenomenon occurs due to diffraction of external real-world and stray light
Solution Approach 1:
The patent converts the harmful rainbow effect caused by diffraction of external light into a beneficial filtering mechanism. By designing the out-coupling DOE with polarization-sensitive grating structures, the system selectively diffracts only TE-polarized virtual image light while allowing TM-polarized external real-world light to pass through without diffraction, thus eliminating rainbows while maintaining light control flexibility
Solution Approach 2:
The patent changes the polarization state parameter of light to resolve the contradiction. A polarizing filter is introduced at the front of the system to ensure incoming real-world/stray light is TM-polarized, while the out-coupling DOE is configured to be sensitive only to TE-polarized light. This parameter differentiation allows the system to distinguish between virtual image light and external light, enabling selective diffraction and eliminating rainbow artifacts
2Reliability
If polarization-sensitive grating is used to eliminate rainbows, then image clarity is improved, but device complexity increases due to additional polarizing filter and polarization-sensitive DOE configuration
Solution Approach 1:
The patent merges the polarization filtering function with the diffractive out-coupling function into a single polarization-sensitive grating structure. The out-coupling DOE is designed with grating structures that are inherently sensitive to polarization states, combining what would traditionally be separate components (polarizing filter + diffractive element) into an integrated solution, thus improving image clarity while minimizing additional complexity
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
This configuration effectively reduces or eliminates rainbows in the display by preventing the diffraction of TM-polarized real-world/stray light, enhancing image clarity and user experience in near-eye display systems.
Implementation Method 1
a polarizing filter is utilized in conjunction with a downstream out-coupling DOE that includes diffractive grating structures that are configured to enable sensitivity to an opposite polarization state
Implementation Method 2
The polarization-sensitive out-coupling DOE diffracts the TE-polarized imaging beam out of the grating for display while the TM-polarized light from the real world and/or stray light passes through the grating without diffraction
Data Source
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AI summary
In a near-eye optical display system comprising a waveguide and diffractive optical elements (DOEs) configured for in-coupling, exit pupil expansion, and out-coupling, a rainbow phenomenon manifested in the display may be removed or reduced using a polarizing filter at the front of the system so that real-world/stray light entering the system has a particular polarization state, for example TM-polarized. The polarizing filter is utilized in conjunction with a downstream out-coupling DOE that includes diffractive grating structures that are configured to enable sensitivity to an opposite polarization state, for example TE-polarized. An imager is configured to produce virtual-world images that also have a TE-polarized state. The polarization-sensitive out-coupling DOE diffracts the TE-polarized imaging beam out of the grating for display while the TM-polarized light from the real world and/or stray light passes through the grating without diffraction and thus cannot contribute to rainbows in the display.