Flat-Panel Holographic Display Using Surface Acoustic Wave Gratings
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Solution Overview
Problem
Current holographic video displays face challenges due to limitations in spatial light modulators, including low bandwidth, high cost, poor scalability, and noise issues, which hinder the development of efficient and cost-effective full-color, video-rate holograms with wide view angles.
Innovation Solution
A flat-panel holographic video display utilizing guided-wave electro-optics with surface acoustic wave transducers to create a diffraction grating, allowing for efficient light outcoupling and wavefront curvature formation, enabling the production of holographic images with improved angular deflection and optical efficiency, and incorporating features like nanopatterning and spatial filters for reduced noise and glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional spatial light modulators (LC, MEMS, bulk-wave acousto-optic) are used in holographic video displays, then the display can be constructed, but the bandwidth is low, cost is high, and scalability is poor
Solution Approach 1:
The patent replaces conventional mechanical and electronic spatial light modulators (LC, MEMS) with a guided-wave acousto-optic modulator that uses surface acoustic waves to modulate light. This substitution enables video-rate operation with bandwidth exceeding 1 MHz, resolving the bandwidth limitation of conventional modulators while maintaining a manageable device structure through integrated waveguide technology.
Solution Approach 2:
The patent changes the operating parameters of the spatial light modulator by using guided-wave acousto-optic interaction instead of conventional bulk-wave or electronic modulation. This parameter change enables high bandwidth operation at video rates while reducing device complexity through the use of planar integrated waveguide structures that are more scalable than conventional approaches.
2Reliability
If conventional spatial light modulators are used, then the display can function, but noise and artifacts appear in the display output
Solution Approach 1:
The patent replaces conventional spatial light modulators that generate noise and artifacts with a guided-wave acousto-optic modulator. The surface acoustic wave interaction in the waveguide structure provides clean modulation without the zero-order noise and higher-order diffraction artifacts that plague conventional modulators, thereby improving display quality and reliability.
3Adaptability or versatility
If current modulators are used, then holographic display can be achieved, but diffraction angle is low and view angle is limited
Solution Approach 1:
The patent uses guided-wave acousto-optic modulation where surface acoustic waves propagate along the waveguide surface, creating diffraction gratings that operate in a different dimensional regime than conventional bulk-wave modulators. This enables larger diffraction angles and wider view zones without requiring complex optical path duplications or phase shifting mechanisms.
4Reliability
If conventional approaches are used to compensate for modulator deficiencies, then display performance can be improved, but cost and complexity increase significantly
Solution Approach 1:
The patent extracts and eliminates the need for complex compensatory systems (eye tracking, optical path duplication, phase shifting) by using a guided-wave acousto-optic modulator that inherently provides high bandwidth, wide view angle, and low noise. This extraction of unnecessary components significantly reduces system complexity and cost while maintaining or improving display performance.
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 the creation of transparent, high-refresh-rate, full-color holographic displays with up to 180-degree view zones, low glare, and high optical efficiency, suitable for various applications including augmented reality and consumer electronics, while simplifying fabrication and reducing costs.
Implementation Method 1
an array of surface acoustic wave transducers arranged along an outer surface of the light-guiding substrate, the array being electrically connected to the control layer and configured to produce a diffraction grating comprising surface acoustic waves
Implementation Method 2
the surface acoustic wave diffraction grating causes the waveguide element to outcouple light bouncing within the substrate
Implementation Method 3
causes the waveguide element to outcouple light bouncing within the substrate
Data Source
AI summary
In a method for forming a holographic image, light is provided to a flat-panel holographic video display that includes waveguide elements that each have a light-guiding substrate and an array of transducers configured to produce a diffraction grating comprising surface acoustic waves. The grating causes the waveguide to outcouple light, focusing it to, or producing wavefront curvatures consistent with it having emanated from, one or more points, in order to form a holographic image. The transducer array may include a large number of densely packed, vertically-adjacent transducers for each hogel for full parallax or may include a small number of vertically-adjacent transducers and a cylindrical optical element for each hogel. The display may be edge-illuminated by a collinear multicolor source. The substrate exit face may have nanopatterned areas alternated with flat areas in order to create regions of optimal internal reflection next to regions of low reflection.