Refractive Index Modulation in AR/VR Diffractive Gratings
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Solution Overview
Problem
Current augmented and virtual reality displays face challenges in achieving a wider field of view and higher refractive index while maintaining efficient light propagation, leading to limitations in display performance.
Innovation Solution
The use of diffractive gratings with microheaters and varying refractive index materials to modulate light propagation, allowing for efficient conversion and direction of image beams through optical elements in head-mounted displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the refractive index of the waveguide is increased to achieve a wider field of view, then the field of view is improved, but the design complexity increases and light propagation efficiency decreases
Solution Approach 1:
The waveguide is divided into multiple zones along its length, with each zone having a different refractive index. The refractive index varies gradually from the input end to the output end, allowing localized optimization of light propagation characteristics without requiring the entire waveguide to have uniformly high complexity
Solution Approach 2:
The refractive index parameter is changed continuously along the length of the waveguide rather than being uniform. This gradient in refractive index allows the waveguide to achieve wider field of view while managing design complexity through controlled parameter variation
2Stability of the object's composition
If the refractive index is increased along the length of the waveguide to create more uniform display, then display uniformity is improved, but light loss increases due to less light remaining in the waveguide
Solution Approach 1:
Different zones of the waveguide have different refractive indices optimized for their specific positions. Zones closer to the input have lower refractive indices to maintain light coupling, while zones toward the output have higher refractive indices to maintain uniform display quality, thereby reducing overall light loss while achieving display uniformity
Solution Approach 2:
The refractive index is made dynamic along the length of the waveguide, varying continuously to adapt to the changing light intensity distribution. This dynamic variation ensures that light is retained efficiently throughout propagation while maintaining uniform display output
3Ease of operation
If diffractive gratings are used to direct light in the waveguide, then light direction control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The diffractive grating is segmented into multiple zones corresponding to different waveguide regions. Each segment can be manufactured with standard precision requirements, and the collective effect of all segments achieves the desired light direction control, thereby reducing overall manufacturing precision requirements compared to a single high-precision grating
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
Enhances the efficiency and performance of optical elements in augmented and virtual reality displays by optimizing light distribution and increasing the field of view, while reducing light loss and improving display quality.
Implementation Method 1
a plurality of voltages is applied to the plurality of microheaters to selectively modulate respective refractive indexes of corresponding portions of the diffractive grating
Implementation Method 2
The optical element may comprise a diffractive grating and a plurality of microheaters corresponding to respective portions of the diffractive grating, wherein a plurality of voltages is applied to the plurality of microheaters to selectively modulate respective refractive indexes of corresponding portions of the diffractive grating. The optical element may be configured to convert the image beam into an output image by diffracting the image beam through the diffractive grating
Implementation Method 3
Light propagating inside the waveguide follows Total Internal Reflection (TIR), and the TIR angle is governed by the refractive index of the waveguide
Data Source
AI summary
Head-mounted displays (HMD) or other suitable optical equipment with waveguides comprising an optical element comprising a diffractive grating having a plurality of zones. The plurality of zones may comprise a first zone, a second zone and a third zone. Substantially all of a plurality of structures defining the first zone may comprise a first material, substantially all of a plurality of structures defining the third zone comprises a second material, a plurality of structures defining the second zone comprises each of the first material and the second material, and a refractive index of the second material may be higher than a refractive index of the first material.