Digital Hologram Generation via Omnidirectional Angular Spectrum
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Solution Overview
Problem
Existing methods for generating digital holograms are complex, limited to single objects, and inefficient in managing occultations, requiring significant computational resources and being inflexible in terms of hologram orientation and pixel size.
Innovation Solution
A method for generating digital holograms that calculates an omnidirectional angular spectrum for each object using a geometric solid sampled by a regular grid, allowing for efficient occlusion management and adaptation to multiple objects and varying viewing directions, without requiring a mesh model or complex graph traversal algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If occultation management is done using intersection test between light rays and scene geometry, then realistic visualization is achieved, but computational cost becomes extremely high
Solution Approach 1:
The patent pre-calculates the omnidirectional angular spectrum of the scene and stores it in a data structure. This preliminary computation allows that when a hologram is needed, the system only needs to extract and process pre-computed data rather than performing complex ray-object intersection tests in real-time, thus maintaining realistic visualization while dramatically improving computational efficiency.
Solution Approach 2:
The patent creates a data structure that stores the omnidirectional angular spectrum as a copy of the scene's light field information. Instead of repeatedly performing expensive intersection tests, the system uses this pre-computed spectral representation, which captures all necessary geometric and occlusion information in an efficient format for hologram generation.
2Adaptability or versatility
If omnidirectional angular spectrum is calculated on sphere surface sampled by icosahedron subdivisions, then complete angular coverage is achieved, but graph traversal algorithm complexity increases
Solution Approach 1:
The patent changes the parameter representation from a mesh-based icosahedron subdivision to a regular grid sampling on the sphere surface. This parameter transformation simplifies the data structure and eliminates the need for complex graph traversal algorithms, while maintaining complete angular coverage through the systematic grid arrangement.
3Productivity
If pre-calculation of omnidirectional angular spectrum is done, then real-time hologram derivation is enabled, but reusability for different pixel sizes is limited
Solution Approach 1:
The patent creates a dynamic system where the pre-computed omnidirectional angular spectrum serves as a universal foundation. The hologram generation process dynamically adjusts the spectral data to accommodate different pixel sizes and hologram resolutions by extracting plane waves at different sampling densities from the same pre-computed spectrum, enabling real-time rendering across various display configurations.
4Device complexity
If hologram plane position is restricted to rotation within sphere plane and translation along radius, then calculation simplicity is maintained, but hologram positioning flexibility is reduced
Solution Approach 1:
The patent extends the hologram plane positioning beyond the simple sphere surface to arbitrary positions in 3D space. The system dynamically calculates the appropriate plane wave extraction and spectral transformation for any desired hologram location and orientation, maintaining computational efficiency while achieving full positioning flexibility needed for head-mounted display applications.
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 simplifies the generation of high-quality holograms for multiple objects, reduces computational complexity, and enables hologram generation from any position, independent of pixel resolution or size, ensuring efficient real-time rendering in virtual or augmented reality applications.
Implementation Method 1
The omnidirectional angular spectrum of the object corresponds to the decomposition into plane waves of the light field emitted by the object
Implementation Method 2
The hologram is generated by applying an inverse Fourier transform to the propagated spectrum
Implementation Method 3
a calculation method allowing the removal of hidden surfaces in a computer-generated hologram by selecting light rays emitted by various point light sources representing a three-dimensional object according to their geometric position
Data Source
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Figure 3~5A
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AI summary
The invention concerns a method for generating a digital hologram representing a 3D scene comprising at least one object (Obi), an object being defined by a plurality of points and their associated intensity, said method comprising: for each object, a prior step of calculating an "omnidirectional" angular spectrum of the light field emitted by an object in the scene on the surface of a geometric solid centred on said object, a surface of said solid being sampled according to a predetermined grid, a sample of the grid beingassociated with a frequency vector (f = (f x , f y , f z )); for the scene, the following steps: - obtaining a pose (Pu) of an observer in the world frame of reference (Rm); - deriving the hologram (H) from the scene as a function of the pose obtained from the "multidirectional" angular spectra (SAi) calculated for each object. The invention is characterised in that the step of calculating an angular spectrum of the light field for each object of the scene takes into account a plurality of predetermined viewing directions (Vj).