Angle-Multiplexed Volume Holographic Optical Elements for Ghost Noise Control
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Solution Overview
Problem
Volume holographic optical elements suffer from ghost noise due to light coupling between different gratings after angle multiplexing, causing images to appear at unintended positions.
Innovation Solution
Designing volume gratings with identical horizontal components and periods to ensure consistent diffraction angles, preventing light from entering incorrect gratings and avoiding ghost noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the number of volume gratings is increased to expand the visible angle through angle multiplexing, then the visible angle for observing images is improved, but ghost noise occurs due to coupling of light by volume gratings of different periods
Solution Approach 1:
The patent applies local quality by making the horizontal grating periods of different volume gratings equal while their vertical periods differ. This localized parameter uniformity (horizontal equality) prevents cross-coupling between gratings while maintaining angle multiplexing capability, thus expanding visible angle without generating ghost noise.
Solution Approach 2:
The patent changes the grating period parameters by setting horizontal periods equal across all volume gratings while allowing vertical periods to differ. This parameter configuration ensures that light diffracted by one grating cannot satisfy the diffraction condition for other gratings, eliminating ghost noise while preserving multi-angle functionality.
2Adaptability or versatility
If volume gratings with different periods are used for angle multiplexing, then target rays can diffract at various angles, but light may enter incorrect gratings resulting in images appearing at unintended positions
Solution Approach 1:
The patent makes the horizontal grating periods equal across all volume gratings while maintaining different vertical periods. This creates a selective diffraction condition where only the intended grating can diffract light at the required angle, ensuring precise image positioning while maintaining angle multiplexing versatility.
Solution Approach 2:
The patent introduces asymmetry in the vertical grating periods while maintaining symmetry in horizontal periods. This asymmetric configuration ensures that each grating has a unique diffraction characteristic in the vertical direction, preventing cross-talk between gratings and ensuring accurate image positioning at different angles.
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
Ensures accurate image projection at the target position by eliminating ghost noise, enhancing image visibility and reducing environmental sensitivity.
Implementation Method 1
the light processed by the volume grating G1 should diffract within the light guide and enter the volume grating H1 of the exit volume holographic optical element
Data Source
AI summary
The present invention relates to volume holographic optical elements to avoid ghost noise. The volume holographic optical element comprises a plurality of volume gratings, which correspond to different incident angle lights, respectively, and have vectors designed with identical components horizontal to an incident interface and possess identical grating periods horizontal to the incident interface. When a device (e.g., head-mounted display) associated with volume holographic optical technology employs the volume holographic optical technology designed by the present invention, angle multiplexing by the volume holographic optical element enables overlapping of images coupled in and out of light guide through different gratings, thereby avoiding the occurrence of ghost noise.