Head-Up Display Waveguide with Separate Grating
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Solution Overview
Problem
The manufacturing of optical waveguides for head-up displays is hindered by irregularities and stress induced during the formation of output coupling structures, leading to poor optical performance and increased costs.
Innovation Solution
A method involving a separate formation and attachment of a reflective output coupling structure, such as a graded saw-tooth grating, onto the waveguide body using a transmissive material cured with UV light, reduces mechanical processing and stress, improving image quality and manufacturing efficiency.
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 into a distinct component. The reflective structure is formed separately and then attached to the waveguide surface, avoiding direct mechanical processing of the waveguide itself. This segmentation eliminates stress-induced optical distortions while maintaining the light redirection function.
Solution Approach 2:
An adhesive layer acts as an intermediary between the waveguide body and the reflective structure. This adhesive mediator allows the reflective structure to be attached without direct mechanical contact or stress transfer to the waveguide, preserving optical quality while enabling structural attachment.
2Ease 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 the cost and time for manufacture increase
Solution Approach 1:
By forming the reflective structure separately from the waveguide, each component can be manufactured independently using optimized processes. The waveguide can be produced via injection molding or other efficient methods, while the reflective structure can be created separately and attached, reducing overall manufacturing complexity and cost.
Solution Approach 2:
The reflective structure is prepared in advance as a separate component before attachment to the waveguide. This preliminary formation allows for pre-processing and quality control of the reflective element independently, streamlining the final assembly process and reducing overall manufacturing time.
3Ease of operation
If mechanical processing is used to form the output coupling structure, then the light can be redirected, but distortions and stresses are introduced reducing image quality
Solution Approach 1:
The mechanical processing method is replaced with a combination of deposition and curing processes. Instead of mechanically stamping or engraving the waveguide surface, an optically transmissive material is deposited and then cured to form the reflective structure, eliminating mechanical stress and distortion while achieving the same light redirection function.
Solution Approach 2:
The material state is changed from solid (mechanical processing) to liquid/gel (deposition) and then to cured solid (curing). This parameter change allows the reflective structure to be formed without mechanical contact or stress application to the waveguide, preserving optical quality while achieving the desired light redirection.
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 enhances image quality and reduces manufacturing costs by minimizing distortions and stresses in the waveguide, increasing yield and allowing for additional optical coatings to optimize light propagation.
Implementation Method 1
The curing step may comprise exposing the transmissive material to UV light
Implementation Method 2
Ray 13 then propagates along the length of the waveguide, guided by total internal reflection at the surfaces of the waveguide
Implementation Method 3
the output coupling structure is a reflective structure configured to direct light out of the optical waveguide by reflection
Data Source
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. In a method of manufacture for such a waveguide the output coupling structure may be formed by depositing a material on a main waveguide, impressing the reflective structure into that material, and curing the material.