Waveguide Pupil Expander Structure for Breakage Integrity Detection
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Solution Overview
Problem
Existing waveguide pupil expanders in holographic projection systems are prone to mechanical, structural, and optical failures due to breakage, which compromises the integrity and functionality of the system.
Innovation Solution
A layered glass structure is used in the waveguide pupil expander, comprising at least one glass layer and another optically transparent layer, such as a polymer-based layer or resin layer, to maintain structural and functional integrity by keeping reflective surfaces parallel even in the event of breakage, and a viewer tracking system detects stray light to signal failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional glass waveguide pupil expander is used, then the optical performance is good, but the structural integrity is compromised due to breakage
Solution Approach 1:
The waveguide pupil expander uses a composite structure combining glass layers with polymer-based or resin-based layers. The glass layers provide optical performance while the polymer/resin layers provide flexibility and resistance to breakage, creating a composite material structure that resolves the contradiction between optical quality and structural integrity
Solution Approach 2:
The patent introduces flexible polymer-based or resin-based layers within the waveguide structure. These flexible layers act as shock-absorbing elements that prevent complete failure when the glass components are subjected to impact, maintaining structural integrity while preserving optical functionality
2Reliability
If glass layers are used in the waveguide, then the optical transparency is good, but the device is prone to breakage
Solution Approach 1:
The patent incorporates polymer-based or resin-based layers beforehand within the waveguide structure to cushion and absorb impact energy before it can damage the glass layers. This preemptive cushioning protects the optically transparent glass components from impact damage while maintaining overall functional integrity
3Reliability
If the waveguide maintains parallel reflective surfaces, then the light guidance is efficient, but the structure is rigid and vulnerable to breakage
Solution Approach 1:
The patent introduces flexible polymer-based or resin-based layers that can deform under mechanical stress while maintaining the parallelism of reflective surfaces. This flexibility allows the structure to withstand impact without breaking, while the maintained parallelism ensures continued efficient light guidance
Solution Approach 2:
The composite structure combines rigid glass layers with flexible polymer/resin layers, creating a hierarchy where the flexible layers absorb mechanical stress and maintain surface parallelism, while the glass layers provide optical functionality. This resolves the contradiction between structural rigidity for light guidance and flexibility for damage resistance
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 layered glass structure ensures continued functionality of the waveguide pupil expander by maintaining parallelism and guiding light to the viewing area despite breakage, while the viewer tracking system promptly responds to failures by controlling the light source, thus preserving image quality and safety.
Implementation Method 1
The waveguide pupil expander comprises a glass structure... The pair of parallel reflective surfaces is arranged to guide the spatially-modulated light from the input port to the output port by a series of internal reflections
Implementation Method 2
The pair of parallel reflective surfaces is arranged to guide the spatially-modulated light from the input port to the output port by a series of internal reflections
Data Source
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Figure 2B
AI summary
A system and method includes a display device comprising a spatial light modulator arranged to output spatially modulated light to form an image. The system further includes a waveguide pupil expander configured to receive spatially modulated light from the display device at an input port thereof and to expand the viewing window of the system. The system further comprises a controller and a viewer tracking system. The viewer tracking system is arranged to monitor a viewer's face to detect stray light incident thereon, and to output a signal indicating a mechanical, structural or optical failure of the waveguide pupil expander upon detection thereof. The controller is arranged to respond to a signal indicating a mechanical, structural or optical failure of the waveguide pupil expander. In examples, the controller is configured to control the spatially modulated light output by the display device, such as to control (e.g., turn off) a light source of the display device, in response to a signal indicating detection of the breakage of glass.