Leaky-Mode Waveguide Spatial Multiplexing for Wide-Angle Projection
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Solution Overview
Problem
Leaky-mode acousto-optical modulators in visual displays have a limited field of view (FOV) that typically does not exceed 10 degrees, which is inadequate for wide-angle applications.
Innovation Solution
The FOV is extended by employing spatial and/or temporal multiplexing techniques using an array of transducers coupled to a waveguide, combined with reflectors such as volume Bragg gratings, to redirect out-coupled light portions at different angles, creating a larger, continuous synthetic FOV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If leaky-mode acousto-optical modulators are used, then device complexity is reduced, but field of view range is limited to typically not exceeding 10 degrees
Solution Approach 1:
The waveguide is divided into multiple sections, each with a different grating period. Each section corresponds to a specific angular range of the field of view. By segmenting the waveguide into zones with different acoustic modulation characteristics, the system achieves a wider overall FOV while keeping each segment relatively simple in design.
Solution Approach 2:
Different portions of the waveguide are assigned different local properties, specifically different grating periods tailored to specific angular ranges. This allows each local region to optimize for its intended viewing angle, with the first portion handling one angular range and the second portion handling another, thereby expanding the total FOV without requiring complex centralized optics.
2Adaptability or versatility
If complex image generation and projection systems are used, then field of view range is extended, but device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical beam scanning systems and complex projection optics with an acousto-optical approach. Acoustic waves are used to modulate the refractive index in the waveguide, creating dynamic diffraction gratings that steer light beams without any moving mechanical parts. This substitution maintains wide FOV capability while dramatically reducing device complexity.
Solution Approach 2:
The system changes the grating period parameter dynamically by applying acoustic waves of different frequencies and amplitudes to different portions of the waveguide. By modulating the refractive index through acoustic excitation, the effective grating period can be tuned to direct light at different angles, achieving wide FOV coverage without complex mechanical adjustment 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
This approach enables the generation of a wide-angle visual display by overlapping FOV portions, allowing for a larger, continuous field of view suitable for diverse applications.
Implementation Method 1
Each transducer is configured to provide, responsive to a driving signal, an acoustic wave in the waveguide. The acoustic wave excites a leaky mode of propagation of the light beam in the waveguide, resulting in out-coupling of a portion of the light beam from the waveguide.
Data Source
AI summary
A leaky-mode acousto-optical modulator may be used to generate visual images suitable for direct viewing, without image-forming optics. To extend a field of view of the modulator to limits suitable for visual displays, an array of acoustic transducers is coupled to a waveguide along its length. Each acoustic transducer generates an acoustic wave causing a corresponding leaky mode to appear. A reflector is disposed proximate each transducer for directing the out-coupled light portion at a unique angle, providing a corresponding field of view portion for that direction. The field of view portions coalesce into a continuous synthetic field of view suitable for wide-angle visual display applications.