Acousto-Optic Holographic Display for Scalable AR
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Solution Overview
Problem
Current spatial light modulators for holographic video displays face challenges such as low bandwidth, high cost, poor scalability, and noise issues, making them unsuitable for large, high-quality holographic displays.
Innovation Solution
A transparent holographic video display system utilizing monolithic guided-wave acousto-optics with integrated volume gratings and space-multiplexed elemental modulators that exploit leaky-mode diffraction, featuring anisotropic waveguides and surface acoustic wave transducers to produce a fully-monolithic, scalable, and cost-effective solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid crystal or MEMS spatial light modulators are used in holographic displays, then spatial light modulation is achieved, but bandwidth is limited and cost increases
Solution Approach 1:
The patent replaces mechanical spatial light modulators (LC and MEMS devices) with an acousto-optic modulator that uses sound waves to modulate light. This substitution eliminates the mechanical moving parts and material limitations of LC and MEMS technologies, achieving higher bandwidth (greater than 100 MHz) while reducing device complexity through a more straightforward acoustic modulation mechanism.
Solution Approach 2:
The patent changes the fundamental operating parameters by using acoustic waves instead of electrical or mechanical fields for light modulation. The acousto-optic modulator uses sound wave frequency and amplitude to control light diffraction, enabling bandwidth exceeding 100 MHz compared to the limited bandwidth of conventional LC and MEMS modulators, while simplifying the overall system architecture.
2Area of stationary object
If arrays of spatial light modulators are added to increase display size, then display area increases, but device complexity and cost increase
Solution Approach 1:
The patent transitions from a two-dimensional array of spatial light modulators to a one-dimensional acousto-optic modulator configuration. By using the acoustic wave propagation direction and time-multiplexing techniques, the system achieves large display areas without requiring complex two-dimensional arrays, thereby reducing device complexity and cost while maintaining scalability.
Solution Approach 2:
The patent introduces dynamic time-multiplexing control to the acousto-optic modulator, where different regions of the display are activated sequentially at high speeds. This dynamic approach enables large display areas to be achieved with a single modulator element rather than requiring static arrays, significantly reducing device complexity while maintaining large display dimensions.
3Reliability
If conventional spatial light modulators are used, then light modulation is achieved, but noise and artifacts appear in display output
Solution Approach 1:
The patent replaces conventional spatial light modulators with an acousto-optic modulator that uses acoustic waves to modulate light. This substitution eliminates the optical non-idealities, quantization errors, and noise artifacts inherent in LC and MEMS devices, resulting in cleaner display output with fewer artifacts and improved overall reliability of the holographic display.
4Adaptability or versatility
If eye tracking is added to compensate for low diffraction angle, then view angle is improved, but device complexity increases
Solution Approach 1:
The patent fundamentally changes the diffraction parameter by using acousto-optic modulation instead of conventional spatial light modulation. This parameter change naturally produces larger diffraction angles without requiring additional eye-tracking compensation systems, thereby improving view angle while avoiding the added complexity of eye-tracking hardware and control systems.
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 high-quality, scalable, and cost-effective holographic video displays suitable for near-to-eye and see-through augmented reality applications, with improved diffraction efficiency and reduced noise, achieving wide angular acceptance and full-color operation without additional supporting optics.
Implementation Method 1
each of which exploit leaky-mode diffraction of guided-mode light
Implementation Method 2
all reflection volume gratings operate in the Bragg regime, thereby creating no dispersion of ambient light
Implementation Method 3
at least one surface acoustic wave transducer spaced along the length of the waveguide
Data Source
AI summary
A holographic display is comprised of space-multiplexed elemental modulators, each of which consists of a surface acoustic wave transducer atop an anisotropic waveguide. Each “line” of the overall display consists of a single anisotropic waveguide across the display's length with multiple surface acoustic wave transducers spaced along the waveguide length, although for larger displays, the waveguide may be divided into segments, each provided with separate illumination. Light that is undiffracted by a specific transducer is available for diffraction by subsequent transducers. Per transducer, guided-mode light is mode-converted to leaky-mode light, which propagates into the substrate away from the viewer before encountering a volume reflection grating and being reflected and steered towards the viewer. The display is transparent and all reflection volume gratings operate in the Bragg regime, thereby creating no dispersion of ambient light.