SAW Modulator Exit Angle Expansion via Intermediary Optics
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Solution Overview
Problem
Existing electro-holographic 3D displays using surface acoustic wave (SAW) modulators have limitations, particularly in achieving a high exit angle for the fan of light, which restricts the field of view and image quality due to small deflection angles and limited spatial frequency capabilities.
Innovation Solution
The solution involves augmenting SAW modulators with optical enhancements, such as angled end faces and transmissive or refractive optics, to increase the exit angle of the fan of light, and using a method that couples light into a waveguide, generates surface acoustic waves, and conditions the exiting light with optics to form a beam, focus, or create diverging light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional SAW modulators are used, then the device structure is simple, but the exit angle of the fan of light is limited and the field of view is restricted
Solution Approach 1:
The patent introduces an intermediary optical system comprising a first lens, a second lens, and a diffuser positioned between the SAW modulator and the observer. This intermediary system transforms the limited exit angle light from the modulator into a wide field of view by creating a virtual image that appears to originate from a different angular position, thereby resolving the contradiction between simple device structure and wide field of view requirement
Solution Approach 2:
The patent transforms the one-dimensional limitation of exit angle at the modulator plane into a three-dimensional virtual image space. By using the lens system to create a virtual image at a different spatial location and angle, the system effectively adds dimensional transformation, allowing observers to view the display from wide angles without modifying the fundamental SAW modulator structure
2Area of stationary object
If pixel-based spatial light modulators are used, then the modulator area can be increased, but the space-bandwidth product remains low due to large pixel size relative to light wavelength
Solution Approach 1:
The patent replaces the mechanical pixel-based modulation approach with an acousto-optic modulation system. Instead of using physically large pixels that limit spatial frequency, the invention uses surface acoustic waves with wavelengths much smaller than optical wavelengths to modulate light, achieving high spatial frequency capability while maintaining large modulator area through the continuous wave interaction region
Solution Approach 2:
The patent changes the fundamental modulation parameter from physical pixel dimensions to acoustic wave properties. By controlling the frequency, amplitude, and phase of surface acoustic waves rather than discrete pixel states, the system achieves high spatial frequency response (line pairs per millimeter) independent of the physical modulator area, resolving the contradiction between area and precision
3Volume of moving object
If acousto-optical modulators with small deflection angles are used, then the device can be compact, but the exit angle fan is limited and image quality deteriorates
Solution Approach 1:
The patent introduces an intermediary optical relay system that takes the compact small deflection angle output from the acousto-optical modulator and transforms it into a large exit angle fan. The lens system magnifies the angular spread of light without requiring a large modulator volume, thereby maintaining device compactness while achieving high image quality through the angular expansion provided by the optical intermediary
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 angular extent of the exit light, enhancing the field of view and image quality beyond the limitations of conventional SAW modulators, allowing for a more compact and high-quality 3D display.
Implementation Method 1
a waveguide, patterned on an optical substrate, carries a time-varying diffracting region that is formed by index changes due to the substrate's piezoelectric effect under radio frequency (RF) excitation
Implementation Method 2
The surface acoustic wave interacts with input light and thereby causes at least some of the light to change from a guided mode within the waveguide to a leaky mode that exits the waveguide
Implementation Method 3
an optic is provided on this exit face... the optic is used to increase an exit angle fan of the light from the substrate
Data Source
AI summary
An electro-holographic light field generator device is disclosed. The light field generator device has an optical substrate with a waveguide face and an exit face. One or more surface acoustic wave (SAW) optical modulator devices are included within each light field generator device. The SAW devices each include a light input, a waveguide, and a SAW transducer, all configured for guided mode confinement of input light within the waveguide. A leaky mode deflection of a portion of the waveguided light, or diffractive light, impinges upon the exit face. Multiple output optics at the exit face are configured for developing from each of the output optics a radiated exit light from the diffracted light for at least one of the waveguides. An RF controller is configured to control the SAW devices to develop the radiated exit light as a three-dimensional output light field with horizontal parallax and compatible with observer vertical motion.