Holographic Reconstruction via Observer Window Wavefront Back-Transformation
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Solution Overview
Problem
Conventional electro-holographic displays face challenges in achieving large viewing angles and high-quality hologram reconstruction due to the mismatch between parallax information and eye accommodation, requiring high-resolution spatial light modulators (SLMs) and significant computational resources, while also struggling with the complexity of encoding and the periodic repetition of hologram patterns leading to multiple reconstructions of the same object points.
Innovation Solution
The method involves determining wavefronts at the observer's eye position for a real object and back-transforming these wavefronts to encode the hologram, using a small observer window and efficient computational approaches such as Fresnel and Fourier transforms to reduce the computational load and avoid multiple reconstructions, allowing for a smaller SLM with lower resolution to produce high-quality holograms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electro-holographic displays use high-resolution spatial light modulators to achieve large viewing angles and high-quality hologram reconstruction, then the viewing angle and reconstruction quality are improved, but the device complexity and computational resource requirements increase significantly
Solution Approach 1:
The patent segments the holographic display into multiple sub-displays arranged in a matrix configuration. Each sub-display contains multiple sub-pixels that can be independently controlled. This segmentation allows the system to achieve large viewing angles and high reconstruction quality without requiring each individual SLM to have extremely high resolution, as the collective arrangement of multiple lower-resolution sub-displays provides the necessary overall resolution and viewing characteristics.
2Adaptability or versatility
If conventional methods encode holograms for large viewing angles, then the viewing angle increases, but multiple reconstructions of the same object points occur due to periodic repetition of hologram patterns
Solution Approach 1:
The patent applies local quality by assigning different encoding characteristics to different regions of the holographic display. Specifically, adjacent sub-pixels or sub-displays use different phase encoding schemes or different portions of the holographic spectrum. This local variation in encoding prevents the periodic repetition that causes multiple reconstructions, as each local region contributes differently to the overall wavefront, ensuring that object points are reconstructed uniquely while maintaining large viewing angles.
3Reliability
If high-resolution spatial light modulators are used to reduce periodic repetition effects, then the number of reconstructions is reduced, but the hardware cost and computational load increase
Solution Approach 1:
By segmenting the holographic display into multiple sub-displays with lower individual resolutions, the computational load for generating and processing holographic data is distributed across multiple simpler units rather than requiring one extremely high-resolution SLM. This segmentation maintains reconstruction uniqueness through proper phase encoding while reducing the computational power needed compared to a single high-resolution device.
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 reduces the computational requirements and hardware costs by enabling high-quality hologram reconstruction with a smaller SLM, allowing for larger viewing angles and minimizing the occurrence of multiple object reconstructions, thus improving the efficiency and effectiveness of hologram generation.
Implementation Method 1
the pixels reconstruct object points by electronically affecting the amplitude and/or phase of an illuminating light
Implementation Method 2
the wave fields interfere in a way that leads to the reconstructed object being visible to the observer
Implementation Method 3
a first Fresnel diffraction is performed for propagating light waves from the hologram plane to the observer plane
Implementation Method 4
a Fast Fourier Transformation is performed to transform the light wave distribution from one plane into another plane
Data Source
AI summary
A method of computing a hologram by determining the wavefronts at the approximate observer eye position that would be generated by a real version of an object to be reconstructed. In normal computer generated holograms, one determines the wavefronts needed to reconstruct an object; this is not done directly in the present invention. Instead, one determines the wavefronts at an observer window that would be generated by a real object located at the same position of the reconstructed object. One can then back-transforms these wavefronts to the hologram to determine how the hologram needs to be encoded to generate these wavefronts. A suitably encoded hologram can then generate a reconstruction of the three-dimensional scene that can be observed by placing one's eyes at the plane of the observer window and looking through the observer window.