Switchable Diffractive Eyepiece for Compact AR Light Coupling
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Solution Overview
Problem
Existing augmented reality eyepieces require large and costly optics to couple image-wise modulated light into multiple waveguides, leading to image quality degradation at the periphery and increased size, which is undesirable.
Innovation Solution
Incorporation of switchable diffractive optical elements, such as dynamically actuable diffractive optical devices, that can selectively couple light into waveguides by switching between different diffraction orders using electromechanical transducers, electrostatic MEMS comb drives, shape memory alloys, or thermal expansion, allowing efficient light routing without enlarging the eyepiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional reflective and refractive optical elements are used to couple light into multiple waveguides, then light coupling efficiency is achieved, but the size and cost of the eyepiece increases
Solution Approach 1:
The patent uses diffractive optical elements with wavelength-scale surface relief structures that change the diffraction parameters dynamically through electrowetting, allowing efficient light coupling without requiring large conventional optical elements. The periodic structure period is on the order of the wavelength of light, enabling compact design while maintaining coupling efficiency.
Solution Approach 2:
The patent replaces conventional mechanical optical elements (reflective and refractive components) with a diffractive optical element that uses electromagnetic fields (electrowetting) to control light routing. This substitution eliminates the need for bulky mechanical optics while achieving the same light coupling function.
2Adaptability or versatility
If multiple waveguides with different diverging field curvatures are used to improve 3D illusion, then virtual object realism is improved, but device complexity increases
Solution Approach 1:
The patent employs a single diffractive optical element that can dynamically perform multiple functions by switching between different diffraction orders. This single element replaces what would otherwise require multiple separate optical components, reducing device complexity while maintaining the ability to provide different diverging field curvatures for improved 3D illusion.
Solution Approach 2:
The patent uses dynamically switchable diffractive optical elements that can change their optical function in real-time through electrowetting. This dynamic capability allows a single element to provide multiple diverging field curvatures as needed, eliminating the need for static multiple waveguides and reducing overall system complexity.
3Weight of moving object
If diffractive optical elements with wavelength scale surface relief structures are used, then lighter weight optics are achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses periodic surface relief structures with periods on the order of the wavelength of light, which can be manufactured using established photolithography and etching techniques. By optimizing the period and depth parameters, the patent achieves the desired optical function with manufacturable precision levels while maintaining lightweight construction.
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
Enables efficient light coupling into multiple waveguides while maintaining image quality and reducing the size and cost of augmented reality eyepieces, providing a more realistic 3D illusion with reduced eye strain.
Implementation Method 1
A diffraction grating is an optical component that deflects light by an angle that is dependent on the wavelength of light and the angle of incidence on the grating
Implementation Method 2
The insulator layer has a first surface facing the quantity of fluid and a second surface facing the diffractive grating. The electrowetting actuator is positioned between the insulator layer and the quantity of fluid and is configured to change a wetting property of the first surface of the insulator layer
Implementation Method 3
forcing the fluid 1030 into the groves 1011 of the grating 1004. The fluid 1030 has an index of refraction that substantially matches with an index of refraction of the transmission diffraction grating 1010 such that forcing the fluid 1030 into the grooves 1011 reduces or eliminates diffraction of light incident on the grating 1004 into higher diffraction orders
Data Source
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AI summary
A dynamically actuable diffractive optical element (DOE) includes a substrate and a diffraction grating disposed on a first region of a surface of the substrate. The DOE further includes a quantity of a fluid disposed on a second region of the surface of the substrate, a fluid displacer disposed adjacent the second region of the surface of the substrate, and a drive signal source configured to send an electric signal to the fluid displacer. The fluid displacer is configured to, upon receiving the electric signal in a first state, causing a portion of the quantity of the fluid to be displaced from the second region of the surface into grooves of the diffraction grating, and upon receiving the electric signal in a second state, causing the portion of the quantity of the fluid to retract from the grooves of the diffraction grating to the second region of the surface.