Single-Waveguide Color Display Optics for Large Field-of-View
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Solution Overview
Problem
Existing near-eye displays face challenges in providing full-color images with a large field-of-view while maintaining a compact and lightweight design, as multi-waveguide solutions are bulky and heavy, and single-waveguide solutions with high refractive index increase weight and thickness.
Innovation Solution
A display optic device using a single slab waveguide with a dual-grating in-coupler that splits light into two directions, each grating configured for different polarizations and angles of incidence, allowing for efficient propagation of visible spectrum light, and expanders to enhance the field-of-view, while using low refractive index materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multi-waveguide solutions are used to provide full-color images with large field-of-view, then the field-of-view and color transmission are improved, but the device becomes bulky and heavy
Solution Approach 1:
The patent combines multiple waveguide functions into a single waveguide structure. The first and second gratings are integrated into one waveguide, allowing multiple wavelengths (RGB colors) to be coupled simultaneously. This merging approach maintains the large field-of-view capability while reducing the number of separate waveguide components, thereby decreasing device weight and bulk.
Solution Approach 2:
The single waveguide is designed to perform multiple functions: it couples light for red, green, and blue wavelengths simultaneously through different grating structures, and guides light in multiple directions. This multi-functional design eliminates the need for separate waveguides for different colors, reducing overall device weight while maintaining full-color capability and large field-of-view.
2Area of stationary object
If high refractive index waveguides are used to increase field-of-view, then the field-of-view is improved, but the waveguide thickness and weight increase
Solution Approach 1:
The patent changes the refractive index parameter by using a low refractive index waveguide material instead of high refractive index materials. This parameter change allows achieving large field-of-view through optimized grating designs and light coupling angles rather than relying on high refractive index, thereby reducing waveguide thickness and weight.
Solution Approach 2:
The patent applies different grating structures (first grating for red wavelength, second grating for green and blue wavelengths) at specific locations within the waveguide to optimize light coupling for different colors. This localized optimization allows the use of low refractive index material while maintaining large field-of-view through precise angular control of light coupling.
3Weight of stationary object
If a single waveguide is used to reduce weight, then the device weight is reduced, but providing large field-of-view for full color becomes difficult
Solution Approach 1:
The patent segments the light coupling function into multiple gratings within a single waveguide: a first grating for red wavelength light and a second grating for green and blue wavelengths. This segmentation allows different wavelength ranges to be coupled at different locations and angles within the same waveguide, achieving full-color capability and large field-of-view while maintaining device weight reduction.
Solution Approach 2:
The patent utilizes angular dimension for light coupling by designing gratings that couple light at different angles of incidence. The first grating couples red light at one angle range while the second grating couples green and blue light at different angle ranges. This angular dimensionality allows multiple color channels to coexist in a single waveguide without spatial interference, maintaining both weight reduction and large field-of-view.
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
Enables a compact and lightweight near-eye display with a large field-of-view for full-color images, improving user comfort and image quality by maintaining color information and reducing weight and size.
Implementation Method 1
a first grating configured to couple light of a first polarization and a first range of angles of incidence of light into the waveguide, wherein the first range comprises angles of incidence of light larger than a threshold angle
Implementation Method 2
a second grating configured to couple light of a second polarization and a second range of angles of incidence of light into the waveguide, wherein the second polarization is perpendicular to the first polarization and wherein the second range comprises angles of incidence around and including normal incidence
Implementation Method 3
Light coupled into the plane may be guided in all directions within a plane, for example by being reflected on inner walls of the waveguide by total internal reflection. The light may be propagated in a slab waveguide by total internal reflection with very little light losses
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
According to an aspect there is provided a display optic device for a near-eye display, configured to receive light representing an image to be displayed to an eye, to guide the light in the display optic device, and to output the light from the display optic device towards the eye. The display optic device comprises a slab waveguide for guiding light and an in-coupler configured to couple light into the waveguide such that the light is propagated in the waveguide in a first direction and a second direction. The in-coupler comprises: a first grating configured to couple light of a first polarization and a first range of angles of incidence of light larger than a threshold angle, into the waveguide, and a second grating configured to couple light of a second polarization and a second range of angles of incidence of light around and including normal incidence such that the second range is complementary to the first range.