Cascaded Splitting Film Waveguide for Near-Eye Displays
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Solution Overview
Problem
Conventional near-eye display systems face challenges in achieving a large field of view and high exit pupil diameter while maintaining efficient light energy transmittance, which is crucial for both indoor and outdoor applications, as existing solutions either impair comfort with high light energy efficiency or fail to provide adequate brightness for outdoor use.
Innovation Solution
A broadband cascaded splitting film array waveguide with alternating high and low refractive index coatings, arranged between glass substrates, is designed to enhance light transmittance and energy efficiency, allowing for a more uniform and balanced transmittance curve across different angles and wavelengths, thereby improving the display system's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single-piece type coupler is used to achieve a large field of view and large exit pupil diameter, then the field of view and exit pupil diameter are improved, but the volume becomes large and the light energy efficiency decreases
Solution Approach 1:
The patent divides the single-piece coupler into multiple thin film layers (alternating high and low refractive index materials) deposited on a substrate. This segmentation allows the coupler to achieve the required optical functions with much reduced volume while maintaining large field of view and exit pupil diameter through the distributed optical path control across multiple layers.
2Loss of energy
If the efficiency of light energy is increased in a single-piece type coupler, then the light energy efficiency is improved, but the external transmittance decreases and comfort is impaired
Solution Approach 1:
The patent applies local quality by using alternating high and low refractive index materials in specific layer configurations. Each layer pair is designed with specific thicknesses and refractive index ratios to locally control the optical path, achieving high light energy efficiency for virtual images while maintaining high external transmittance for real scenes through localized optical manipulation at each interface.
3Object-affected harmful factors
If the external transmittance is increased in a single-piece type coupler, then the external transmittance is improved, but the light energy efficiency decreases and virtual image brightness is poor
Solution Approach 1:
The patent employs parameter changes by systematically varying the refractive index, layer thickness, and number of layers in the film stack. By optimizing these parameters, the coupler achieves a balance where external transmittance is maximized for comfort while light energy efficiency is maintained through constructive interference effects designed into the specific layer configuration.
4Ease of manufacture
If conventional coating structures are used, then the manufacturing process is simple, but the transmittance curve shows significant fluctuations and uniformity is poor
Solution Approach 1:
The patent uses composite materials by combining multiple layers of high and low refractive index materials in a specific alternating sequence. This composite structure creates a more stable and uniform transmittance curve across different wavelengths and angles compared to conventional single-material coatings, while remaining manufacturable through standard thin film deposition techniques.
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
The solution achieves high uniformity in image brightness across a broad spectrum, exceeding 50% in a 4 mm×4 mm pupil area with minimal attenuation, and reduces the complexity and cost of the design, while maintaining a lightweight and compact structure, effectively addressing the limitations of single-piece couplers.
Implementation Method 1
each film of the splitting film array consists of a plurality of H coatings and L coatings alternately arranged in sequence, wherein the H coatings are coatings made of a high refractive index material, the L coatings are coatings made of a low refractive index material
Implementation Method 2
the display system forms an image at infinity point through a collimating lens, and then reflects the image into the human eyes through a coupler
Data Source
AI summary
The present disclosure provides a broadband cascaded splitting film array waveguide and a display system comprising the same. The cascaded splitting film array waveguide includes a plurality of glass substrates and a splitting film array, each film of the splitting film array is sandwiched between two adjacent glass substrates and consists of a plurality of H coatings and L coatings alternately arranged in sequence, wherein the H coatings are coatings made of a high refractive index material, the L coatings are coatings made of a low refractive index material, each film of the splitting film array has an even number of coatings, and thicknesses an, pn of the coatings of the film are selected based on the band width and angle of the light beam.