Optical Waveguide Full-Color Display Using Segmented Diffraction Gratings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current single-waveguide display devices can only be optimized for one part of the visible spectrum, leading to a strong greenish hue and requiring either limited field of view or multiple waveguides for full-color displays, which increases complexity, cost, and bulk, especially in head-mounted applications.
Innovation Solution
The use of two waveguides with periodic diffraction gratings having different pitches and layered coatings, including a reflective layer, to separately expand and recombine spectral portions of light for each primary color, allowing for a full-color image to be displayed without the need for multiple waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single waveguide is used for display, then the device complexity is reduced, but the display can only be optimized for one part of the visible spectrum resulting in a greenish hue
Solution Approach 1:
The visible spectrum is segmented into two portions: a first spectral portion (e.g., blue-green range) and a second spectral portion (e.g., red-yellow range). Each spectral portion is handled by a separate diffraction grating with different pitch, allowing the single waveguide to process different wavelengths independently and combine them into a full-color display.
2Adaptability or versatility
If three waveguides are used for full color display, then the spectral coverage is improved, but the device complexity, cost, and weight increase
Solution Approach 1:
Two diffraction gratings with different pitches are combined within a single waveguide structure. The first grating handles the first spectral portion while the second grating handles the second spectral portion. Both gratings operate simultaneously within the same waveguide, merging their functions to achieve full-color display without requiring three separate waveguides.
3Adaptability or versatility
If a three-layer stacked volume grating is used, then full color display is achieved, but the manufacturing difficulty and cost increase
Solution Approach 1:
Instead of creating a complex three-layer stacked volume grating, the solution segments the diffraction function into two separate surface gratings with different pitches. Each grating is fabricated independently using standard photolithography techniques, avoiding the need for complex multi-layer stacking and reducing manufacturing difficulty while achieving full-color capability.
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 approach enables a full-color display with reduced complexity and cost, maintaining a compact form factor suitable for head-mounted or helmet-mounted displays by effectively diffracting and transmitting light across a wider field of view for all primary colors.
Implementation Method 1
The first input diffraction region comprises a periodic diffraction grating structure configured to diffract the received light into the first waveguide
Implementation Method 2
a periodic diffraction grating structure having a layered coating configured to increase diffraction efficiency
Implementation Method 3
the layered coating of the second input diffraction region comprises at least one layer of titanium dioxide overlain by the reflective layer comprising a layer of silver
Implementation Method 4
light output from the first waveguide passes through the second waveguide
Data Source
Figure 1a~2b
Figure 3~4b
Figure 5~6
AI summary
An optical method of displaying an expanded colour image comprising extracting from input light bearing said coloured image a first spectral portion and a second spectral portion such that together the two portions contain sufficient information for the image to be displayed in substantially its original colours, separately expanding the two spectral portions each in two dimensions and recombining the expanded spectral portions to display the expanded colour image.