Holographic Waveguide Emission Balancing Without Dielectric Stacks
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Solution Overview
Problem
Conventional holographic projection systems rely on complex dielectric stacks to moderate waveguide emissions, which are difficult to manufacture over a broadband of wavelengths, and require a complex graded coating to compensate for intensity loss during waveguiding.
Innovation Solution
A projection system utilizing a hologram engine that angularly distributes light within a holographic wavefront, compensating for intensity loss by modifying the hologram to account for partial reflection-transmissions at reflective-transmissive surfaces, eliminating the need for complex coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If complex dielectric stacks are used to maintain intensity across waveguide emissions, then intensity uniformity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The hologram is pre-modified to compensate for the intensity loss that will occur during waveguiding. The pattern generator adjusts the diffractive pattern in advance based on the number of reflections each emission zone will undergo, so that when the light is waveguided and intensity loss occurs, the image quality remains uniform.
Solution Approach 2:
The system changes the parameters of the diffractive pattern dynamically based on the waveguiding path. Different emission zones correspond to different numbers of reflections, and the hologram engine adjusts the diffractive pattern parameters to compensate for the corresponding intensity loss at each zone.
2Illumination intensity
If conventional dielectric stacks are used to compensate for intensity loss, then intensity uniformity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces the mechanical/optical solution of precise dielectric stacks with a computational solution. Instead of manufacturing complex optical components with precise thickness control, the system uses a hologram engine to calculate and generate a diffractive pattern that computationally compensates for intensity loss, substituting mechanical precision requirements with computational processing.
3Device complexity
If simple waveguide designs are used, then device complexity is reduced, but intensity uniformity deteriorates
Solution Approach 1:
The hologram acts as an intermediary element between the light source and the waveguide. It pre-compensates for the intensity loss that will occur during waveguiding, allowing simple waveguide designs to achieve uniform intensity output. The hologram absorbs the complexity of intensity compensation in advance, enabling the waveguide itself to remain simple.
4Adaptability or versatility
If optical combiners with curvature are used, then adaptability to vehicle windshields is improved, but image quality uniformity deteriorates
Solution Approach 1:
The system performs preliminary compensation by modifying the hologram before the light reaches the curved optical combiner. The pattern generator calculates the diffractive pattern in advance, accounting for the curvature effects that will occur during waveguiding between the flat hologram and the curved windshield, ensuring uniform image quality is maintained despite the curvature.
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
Enables efficient waveguiding of holographic light without the need for complex coatings, allowing for a compact and cost-effective holographic display system that maintains image quality across a broad spectrum.
Implementation Method 1
The waveguide comprises a pair of parallel reflective surfaces arranged to waveguide the diffracted light field therebetween
Implementation Method 2
A spatial light modulator typically comprises a plurality of individually-addressable pixels which may also be referred to as cells or elements. The light modulation scheme may be binary, multilevel or continuous.
Implementation Method 3
The hologram is arranged to angularly distribute light within the holographic wavefront in accordance with spatial position within the image
Data Source
AI summary
A projection system comprising a display device, a hologram engine and a waveguide. The display device is arranged to display a hologram of an image and spatially modulate light in accordance with the hologram to form a holographic wavefront. The hologram engine is arranged to calculate the hologram. The hologram is arranged to angularly distribute light within the holographic wavefront in accordance with spatial position within the image such that continuous angular ranges of the holographic wavefront respectively correspond with continuous regions of the image. The waveguide comprising a pair of parallel reflective surfaces arranged to waveguide the holographic wavefront therebetween. A first surface of the pair of parallel reflective surfaces is partially reflective-transmissive so as to form an output comprising a plurality of emission zones for the holographic wavefront. The hologram engine is arranged to modify the hologram to at least partially compensate for a decrease in intensity of the emission from each successive emission zone of the waveguide caused by the partial reflection-transmissions at the first surface during waveguiding.