Switchable Diffraction Gratings for Optical Waveguide Displays
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Solution Overview
Problem
Optical waveguides for display devices have a limited field of view due to angular limitations in total internal reflection, which restricts the propagation of light of different wavelengths, leading to reduced visibility of colors outside the specific angular range tuned by the Bragg grating.
Innovation Solution
Incorporating additional switchable diffractive parts before the input diffractive part to redirect light of wavelengths outside the initial field of view to angles that allow total internal reflection, enabling the capture and propagation of light within the waveguide, thereby expanding the color range and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Bragg grating is tuned to a specific wavelength, then light of that wavelength can be propagated along the waveguide within a defined field of view, but light of other wavelengths cannot be captured and propagated effectively
Solution Approach 1:
The input diffractive part is divided into multiple zones, each zone being tuned to diffract a specific wavelength range into the total internal reflection angle range. This segmentation allows the single input diffractive part to handle multiple wavelengths simultaneously, improving wavelength adaptability without adding multiple separate gratings.
Solution Approach 2:
Different zones of the input diffractive part have different local properties (different grating structures) optimized for specific wavelengths. This local quality variation enables each zone to efficiently diffract its corresponding wavelength range while maintaining the overall structure as a single integrated component.
2Adaptability or versatility
If additional diffractive parts are added to expand wavelength coverage, then field of view and color range are improved, but device complexity increases
Solution Approach 1:
Multiple diffractive functions for different wavelengths are merged into a single input diffractive part by creating different zones within it. This combining approach achieves multi-wavelength coverage without requiring multiple separate diffractive components, thus expanding field of view while controlling device complexity.
Solution Approach 2:
The input diffractive part is designed with multi-functionality by incorporating multiple zones that can each handle different wavelengths. This universal design allows one component to perform the work of multiple specialized components, improving adaptability without proportionally increasing 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 solution allows for the expansion of the field of view to include multiple wavelengths, ensuring that all colors are captured and displayed within the same angular range, improving the visibility and spectral coverage of the optical waveguide display.
Implementation Method 1
a first switchable diffractive part switchable between a diffractive state for diffracting light of a first wavelength and a non-diffractive state, and arranged to receive light and selectively to diffract the light
Implementation Method 2
the waveguide to retain light injected into it for propagation along the waveguide by total internal reflection (TIR)
Data Source
AI summary
An apparatus is disclosed for producing an optical display comprising an optical waveguide (1) and a pair (10, 16) of switchable diffraction gratings that are switchable between a diffractive state and a non-diffractive state. A pair of non-switchable diffraction gratings (2, 14) is arranged to receive diffract light from one switchable grating for guided propagation along the optical waveguide and out to the other switchable grating for viewing. The pair of non-switchable gratings are tuned to a first operating wavelength of light, while the pair of switchable gratings are tuned to a different operating wavelength of light to diffract that light into/from a field of view in common with that of the non-switchable gratings such that light of two wavelengths occupies the same field of view.