SAW Optical Modulators with Sense Transducers for 3D Displays
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Solution Overview
Problem
Existing electro-holographic 3D displays using SAW devices have an insufficiently broad exit fan of output light field, with the diffracted output often centered inconveniently away from the normal to the device's exit face, limiting the field of view and failing to achieve the theoretical performance of nearly perfect visual depth information and color rendering.
Innovation Solution
The use of SAW modulators with sense transducers to detect and control surface acoustic waves, allowing for optimized generation and damping of SAWs to increase the exit fan angle, combined with a 'face-fire' configuration of modulators oriented in different directions to broaden the angular field of view, and the implementation of feedback and feedforward circuits for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If SAW modulators are used to deflect light from guided modes, then light deflection capability is improved, but the exit fan angle is insufficient and the output is centered away from the normal to the device exit face
Solution Approach 1:
The patent employs asymmetric configuration of SAW transducers and waveguides to shift the exit fan center from an inconvenient position away from the normal to a desirable position at or near the normal. This involves non-uniform spacing and orientation of transducer elements to create asymmetric diffraction patterns that center the output light field appropriately.
Solution Approach 2:
The patent utilizes multiple dimensions by arranging waveguides and transducers in three-dimensional space with various orientations. By controlling SAW propagation in multiple directions and combining outputs from waveguides at different angles, the system broadens the exit fan angle and centers the output appropriately.
2Adaptability or versatility
If the exit fan angle is increased to broaden field of view, then visual depth information and color rendering are improved, but device complexity increases
Solution Approach 1:
The patent divides the light field generation function into multiple segments by using multiple waveguides, each handling specific angular ranges or wavelength bands. This segmentation allows independent optimization of each waveguide-transducer pair while collectively achieving a broad exit fan angle and high-quality visual output.
Solution Approach 2:
The patent designs the SAW modulator system to perform multiple functions simultaneously: different transducer configurations generate different diffraction angles, some transducers handle wavelength multiplexing, and the system collectively provides both broad field of view and centered output. This multi-functionality reduces the need for separate devices for each function.
3Measurement precision
If sense transducers are added to detect and control SAWs, then SAW generation and damping control are improved, but device complexity increases
Solution Approach 1:
The patent combines the functions of SAW generation and SAW sensing/damping into a unified transducer system. Sense transducers are integrated with drive transducers, and damping functionality is merged with the existing waveguide structure. This consolidation achieves precise SAW control while minimizing the increase in device complexity through functional integration.
Solution Approach 2:
The patent implements feedback control by using sense transducers to detect SAW characteristics and adjusting the drive signal accordingly. This feedback mechanism enables precise control of SAW amplitude and phase, optimizing light diffraction efficiency and enabling active damping of unwanted SAW modes to reduce crosstalk.
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 significantly increases the field of view of diffractive 3D displays, centering the output angle about a convenient direction and broadening the angular field of view, making it more suitable for various applications such as desktop displays, virtual reality, and immersive imagery.
Implementation Method 1
A SAW is generated in a piezoelectric substrate under radio frequency (RF) excitation
Implementation Method 2
This creates a time-varying diffracting region that interact with input light in the waveguide. This causes at least some of the light to change from a guided mode within the waveguide to a leaky mode that exits the waveguide
Data Source
AI summary
An electro-holographic light field generator device comprises surface acoustic wave (SAW) optical modulators arranged in different directions. Specifically, some embodiments have SAW modulators arranged in pairs, nose-to-nose with each other, and have output couplers that provide face-fire light emission. These SAW modulators also possibly include SAW sense transducers and/or viscoelastic surface material to reduce crosstalk.