Stray light control in multi-waveguide combiners

EP4634572A1Pending Publication Date: 2025-10-22GOOGLE LLC
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Patent Information

Application Number
EP2023710505
Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
Filing Date
2023-02-03
Publication Date
2025-10-22

AI Technical Summary

Technical Problem

Multi-waveguide combiners in near-to-eye display devices face issues with stray light paths and crosstalk due to interactions between diffracted orders of gratings, leading to undesirable ray paths and eye safety concerns, which conventional methods like color filters or reflective filters fail to adequately address without increasing complexity or reducing efficiency.

Method used

A waveguide combiner configuration with a diffraction grating situated between stacked waveguides to redirect unwanted light beams into a light trap or absorptive path within the first waveguide, preventing them from entering the second waveguide, while allowing desired wavelengths to pass through, thereby mitigating stray light and crosstalk.

Benefits of technology

This configuration effectively reduces stray light paths and crosstalk between waveguides, improving image quality and eye safety without increasing mechanical complexity or compromising efficiency, by using a diffraction grating to redirect unwanted wavelengths within the waveguide combiner.

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Abstract

A waveguide combiner (200) includes a first waveguide (204-1), a second waveguide (204-2), and a diffraction grating (218). The first waveguide and the second waveguide are disposed in a stacked configuration, with the diffraction grating disposed between the first waveguide and the second waveguide. The diffraction grating is configured to prevent light beams (216-1, 216-2) having wavelengths within a first range of wavelengths from being coupled into the second waveguide, and transmit, to the second waveguide, light beams (216-3) having wavelengths within a second range of wavelengths different from the first range of wavelengths.
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