SAW Modulator Telescopic Optics for Wide Field of View
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Solution Overview
Problem
Current electro-holographic displays using surface acoustic wave (SAW) modulators face limitations in achieving a wide enough exit angle for a full field of view, which restricts the angular extent of diffracted light, making it difficult to create a thin, large-area display with high visual realism.
Innovation Solution
The implementation of a SAW modulator with pixelated demagnification capabilities and volume gratings, along with two arrays of transmissive optics forming a telescopic system, allows for increased exit angles and independence from the position of light diffracted out of the waveguide, enabling thin, large-area displays with improved angular extent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional SAW modulator is used to diffract light, then the device structure is simple, but the exit angle of diffracted light is limited and cannot provide a wide field of view
Solution Approach 1:
The patent divides the single modulator function into multiple components: a SAW modulator for light diffraction and a separate telescopic system with two arrays of transmissive optics for angle expansion. This segmentation allows each component to specialize - the SAW modulator handles light modulation while the telescopic system handles angular expansion, resolving the contradiction between simple structure and wide exit angle.
Solution Approach 2:
The patent introduces a telescopic system as an intermediary between the SAW modulator and the final light output. This intermediary system, consisting of two arrays of transmissive optics, takes the diffracted light from the SAW modulator and expands its angular extent, effectively mediating between the limited exit angle of the modulator and the wide field of view requirement.
2Adaptability or versatility
If the field of view is expanded to provide a wide angular extent, then the visual realism is improved, but the device thickness increases and cannot maintain a thin form factor
Solution Approach 1:
The patent embeds the two arrays of transmissive optics within or near the SAW modulator structure, creating a nested configuration where the telescopic system is integrated into the modulator assembly. This nesting allows the field of view expansion functionality to be incorporated without significantly increasing the overall device thickness, maintaining a thin form factor while achieving wide angular extent.
Solution Approach 2:
Instead of expanding the field of view by increasing device thickness in one dimension, the patent uses the telescopic system to achieve angular expansion through optical path manipulation in multiple dimensions. The two arrays of transmissive optics create a demagnifying telescopic effect that expands the angular extent without proportionally increasing the physical thickness of the device.
3Ease of operation
If a single array of transmissive optics is used for angle expansion, then the device complexity is reduced, but the exit angle cannot be made independent of the light diffraction position
Solution Approach 1:
The patent segments the optical correction function into two distinct arrays of transmissive optics rather than using a single array. This segmentation allows the first array to handle one aspect of angle expansion while the second array handles another aspect, collectively achieving exit angle independence from diffraction position. The two-array configuration provides the necessary degrees of freedom to decouple exit angle from diffraction position.
Solution Approach 2:
The patent uses the two arrays of transmissive optics to introduce parameter changes in the optical path that compensate for variations in light diffraction position. By adjusting the optical parameters through the telescopic system, the exit angle can be made independent of the original diffraction position, achieving the desired ease of operation despite the increased optical configuration complexity.
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 solution significantly increases the exit angle of diffracted light, providing a wider field of view while maintaining a thin form factor, compatible with emitting light from the top or bottom of the modulator, and is tolerant to SAW frequency dispersion and pulse timing errors.
Implementation Method 1
A SAW is generated in a piezoelectric substrate under radio frequency (RF) excitation. This creates a time-varying diffracting region that interacts with input light in a waveguide in the substrate. 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.
Implementation Method 2
One specific device category that provides controllable sub-holograms from which a light field can be constructed uses what is known as a leaky mode surface acoustic wave (SAW) modulator. These devices are a subclass of acousto-optic modulators (AOMs) and generally use acoustic waves to diffract light.
Implementation Method 3
The modulator comprises a substrate and two arrays of transmissive optics for serially conditioning light diffracted in the substrate. The arrays are serial in the sense that light leaving one array enters the other array. In this way the arrays form a telescopic system.
Implementation Method 4
The first array of transmissive optics focuses the light, but in other rare examples, the first array of transmissive optics might cause the light to diverge. Also, one of the arrays could include reflective optics. Preferably, the second array of transmissive optics collimates the light.
Implementation Method 5
The implementation of a SAW modulator with pixelated demagnification capabilities and volume gratings, along with two arrays of transmissive optics forming a telescopic system, allows for increased exit angles and independence from the position of light diffracted out of the waveguide
Data Source
AI summary
Acousto-optical modulators, such as a SAW modulators, with telescope arrays and superimposed volume gratings for light field generation are disclosed. These devices can employ pixelated demagnification and have layers of output optics, such as reflective gratings and/or arrays of transmissive refractive or diffractive lenses that manipulate the light emitted by the SAW modulator. In other cases, superimposed volume gratings are used, in which pixilation occurs in angle space.