Compact HUD Pupil Expander for Diverging Light Field Coupling
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Solution Overview
Problem
Existing display systems face challenges in efficiently coupling and replicating diverging holographic light fields due to the large size requirements of optical components, which limits optical coupling efficiency and compactness.
Innovation Solution
A display system incorporating a coupling element with a reflective-transmissive surface and opposing reflective surface to guide and reduce the size of the holographic light field, coupled with a second replicator to achieve compact two-dimensional pupil expansion, enhancing optical coupling efficiency and reducing component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the holographic light field is directly coupled into the second replicator without size reduction, then the input port of the second replicator must be large to accommodate the expanded light field, but this increases the device footprint and reduces optical coupling efficiency
Solution Approach 1:
A coupling element is introduced as an intermediary component between the first replicator and the second replicator. This coupling element receives the expanded holographic light field from the first replicator and couples it into the second replicator, enabling efficient optical coupling without requiring a large input port on the second replicator. The coupling element acts as a mediator that transforms the light field configuration to match the requirements of the second replicator.
Solution Approach 2:
The coupling element utilizes internal reflection between opposing surfaces to guide the light field, effectively using the third dimension (depth/propagation direction) to manage the light field size. By guiding the light through reflections within the coupling element, the system reduces the required input port size in the transverse dimensions while maintaining efficient coupling.
2Productivity
If conventional optical coupling methods are used for diverging holographic light fields, then the optical components must be large to accommodate the expanded light field, but this increases the overall system size and reduces compactness
Solution Approach 1:
The coupling element serves as a compact intermediary that enables efficient coupling of diverging holographic light fields between replicators. By using internal reflection within a relatively small component, it achieves effective optical coupling without requiring large optical components, thus maintaining both high productivity and compactness.
Solution Approach 2:
The coupling element is designed to be integrated within the overall optical system architecture, nesting the light field management function within a compact structure. The opposing reflective surfaces are positioned close together, creating a space-efficient configuration that reduces the overall volume of optical components while maintaining coupling efficiency.
3Adaptability or versatility
If the holographic light field is guided over a long distance between replicators, then all angular content can be coupled, but this increases the distance required and reduces system compactness
Solution Approach 1:
The coupling element uses internal reflection between opposing surfaces to guide the light field, effectively utilizing the propagation direction (third dimension) to achieve compact light field management. This allows all angular content to be coupled within a short physical distance by using reflections to extend the optical path length without increasing the physical footprint.
Solution Approach 2:
The opposing reflective surfaces in the coupling element create a folded optical path that effectively increases the interaction length between the light field and the coupling structure. This curved/reflected path allows comprehensive angular content coupling within a compact linear distance.
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 enables efficient coupling and replication of diverging holographic light fields, allowing for a more compact design and improved optical efficiency by reducing the size of the input port of the second replicator, thus expanding the viewing area and maintaining uniform intensity across the replicated light field.
Implementation Method 1
a reflective surface, opposing the reflective-transmissive surface, in order to guide at least a portion of the holographic light field by internal reflection therebetween
Implementation Method 2
a first replicator arranged to receive a holographic light field and replicate the holographic light field
Data Source
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AI summary
A display system comprises a two-dimensional pupil expander. The pupil expander comprises a first replicator, a coupling element and a second replicator. The first replicator is arranged to receive a holographic light field and replicate the holographic light field in a first direction. The holographic light field is diverging. The coupling element comprises a reflective-transmissive surface arranged to receive the output of the first replicator and a reflective surface, opposing the reflective-transmissive surface, in order to guide at least a portion of the holographic light field by internal reflection therebetween to an output port of the coupling element and to reduce the size of the holographic light field in a second direction. The second replicator has an input port arranged to receive the output of the coupling element and replicate the holographic light field in the second direction, wherein the second direction is perpendicular to the first direction.