Waveguide Output Coupling Structure for Head-Up Display
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Solution Overview
Problem
Existing waveguides for head-up displays suffer from image distortion due to irregularities in the optical waveguide surfaces, leading to increased manufacturing costs and time.
Innovation Solution
A waveguide system with an output coupling structure that utilizes evanescent wave coupling and an air gap, combined with a reflective structure and optical coatings, to direct light out of the waveguide without mechanical stress, using a saw-tooth grating and UV curing material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the output coupling structure is formed by stamping or engraving into the waveguide surface, then the light can be redirected out of the waveguide, but stress and irregularities are induced in the waveguide leading to poor optical performance
Solution Approach 1:
The output coupling structure is separated from the waveguide body and placed in proximity rather than being directly formed in the waveguide surface. This segmentation allows the coupling structure to be manufactured independently using stamping or engraving techniques without inducing stress or irregularities in the waveguide, thereby maintaining optical performance while enabling light redirection.
Solution Approach 2:
An intermediary coupling structure is introduced that mediates between the waveguide and the external environment. This separate coupling structure interacts with the evanescent field of the waveguide to redirect light without requiring direct mechanical modification of the waveguide surface, thus avoiding stress-induced optical degradation.
2Device complexity
If the output coupling structure is attached directly to the waveguide face, then the structure is simplified, but stress and irregularities are induced leading to poor optical performance
Solution Approach 1:
The device is divided into separate components: the waveguide body and the output coupling structure. The coupling structure is attached in proximity to the waveguide face rather than being integrated directly into it, which simplifies manufacturing by allowing independent fabrication while preventing stress transfer that would degrade optical performance.
Solution Approach 2:
The output coupling structure serves as an intermediary element that couples to the waveguide's evanescent field without direct mechanical contact with the waveguide face. This intermediary approach reduces device complexity by using a separate attachable component while maintaining optical performance through field-based coupling rather than mechanical integration.
3Reliability
If stamping or engraving is used to form the output structure, then the light redirection function is achieved, but the cost and time for manufacture increase
Solution Approach 1:
The output coupling structure is manufactured as a separate component using stamping or engraving techniques, which are then applied to replicate the structure efficiently. This segmentation allows for optimized manufacturing processes and batch production, reducing per-unit cost and time while maintaining the light redirection function.
Solution Approach 2:
The output coupling structure is pre-formed using stamping or engraving techniques before attachment to the waveguide. This preliminary action allows for optimized manufacturing of the coupling structure independently, enabling mass production and reducing overall manufacturing time and cost while ensuring the light redirection function is properly established.
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
Improves image quality and reduces manufacturing costs by minimizing distortions and stress in the waveguide, increasing yield and reducing production time.
Implementation Method 1
an output coupling structure attached to a face of the waveguide body at the output end with an air gap between a region of the output coupling structure and the face of the waveguide body, the air gap being such that light is coupled in that region from the waveguide body to the output coupling structure by evanescent wave coupling
Implementation Method 2
the output coupling structure is a reflective structure configured to direct light out of the optical waveguide by reflection
Implementation Method 3
which light propagates along the waveguide body towards the output end by total internal reflection
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3
AI summary
A waveguide structure for a head up display in which a reflective output coupling structure is formed of a separate, but connected, component to a main waveguide. Light is coupled from the main waveguide to the output coupling structure by evanescent wave coupling. In a method of manufacture for such a waveguide the output coupling structure is attached to the main waveguide using an optical feedback technique.