Waveguide Combiner Grating Layout for Uniform Image Intensity
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Solution Overview
Problem
Existing waveguide combiners suffer from non-uniformities in virtual image propagation due to subtle changes in grating structures and substrate profiles, leading to inconsistent image quality.
Innovation Solution
The waveguide combiner incorporates an input coupling grating, pupil expansion grating, and output coupling grating, along with a pixelated phase modulator or expanders to ensure uniform beam intensity distribution, and a pupil shifting mechanism to adjust beam positions, thereby enhancing image uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional waveguide combiners use standard grating structures for light coupling, then the device complexity is low, but the image uniformity deteriorates due to non-uniform beam intensity distribution
Solution Approach 1:
The waveguide combiner is divided into multiple functional sections with distinct grating structures: input coupling gratings (ICGs) at the first end, pupil expansion gratings (PEGs) in the middle, and output coupling gratings (OCGs) at the second end. Each section has specifically designed grating parameters to perform its function, allowing optimization of image uniformity without requiring complex modifications to the entire device.
Solution Approach 2:
Different grating structures are applied at different locations within the waveguide combiner to address local requirements. The ICGs use first grating structures optimized for input coupling, the PEGs use second grating structures with different periods for pupil expansion, and the OCGs use third grating structures for output coupling. This local differentiation enables uniform beam intensity distribution while maintaining overall device simplicity.
2Manufacturing precision
If the waveguide combiner uses a single grating period throughout, then the manufacturing precision is high, but the beam intensity distribution deteriorates becoming non-uniform across the field of view
Solution Approach 1:
The patent applies different grating periods at different locations: the ICGs have a first period optimized for input coupling, the PEGs have a second period (different from the first) optimized for pupil expansion and uniformity, and the OCGs have a third period optimized for output coupling. This local variation in grating parameters achieves uniform beam intensity distribution while each grating type can be manufactured with standard precision.
Solution Approach 2:
The grating period parameter is deliberately changed at different locations within the waveguide combiner. By varying the period from the first value (ICGs) to the second value (PEGs) to the third value (OCGs), the patent optimizes the beam intensity distribution across the field of view and eyebox, transforming a uniform manufacturing approach into a differentiated parameter strategy.
3Illumination intensity
If the waveguide combiner uses pupil expansion gratings with different periods, then the beam intensity uniformity improves, but the device complexity increases due to multiple grating types
Solution Approach 1:
The device is segmented into three functional zones with distinct grating types: ICGs for input coupling, PEGs for pupil expansion and uniformity control, and OCGs for output coupling. This segmentation allows each component to be optimized independently for its specific function, achieving overall beam intensity uniformity while maintaining clear functional boundaries that simplify design and manufacturing.
Solution Approach 2:
The pupil expansion gratings serve multiple functions: they expand the pupil size to increase the eyebox and simultaneously correct beam intensity non-uniformities. By combining these functions in a single component type with appropriately designed grating periods, the patent reduces the need for additional separate components, thereby managing device complexity while achieving uniformity.
4Ease of manufacture
If conventional waveguide combiners propagate light through standard gratings, then the ease of manufacture is high, but the image quality deteriorates due to non-uniformities from substrate profiles
Solution Approach 1:
The patent addresses image quality issues by applying locally optimized grating structures at specific locations rather than attempting to perfectly control the entire substrate profile. The ICGs, PEGs, and OCGs are designed with specific grating parameters that compensate for typical substrate profile variations in their respective regions, achieving consistent image quality without requiring ultra-precise substrate manufacturing.
Solution Approach 2:
By changing the grating period parameter across different sections (first period for ICGs, second period for PEGs, third period for OCGs), the patent compensates for substrate profile variations and achieves uniform image quality. This parameter differentiation allows standard substrate manufacturing processes to produce high-quality images without requiring complex substrate profile control.
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
The solution achieves uniform intensity distribution of virtual images across the field of view and eyebox, improving the overall image quality and consistency for multiple users.
Implementation Method 1
Light is coupled into and out of waveguide combiners using surface relief gratings
Implementation Method 2
Generated light is in-coupled into a waveguide combiner, propagated through the waveguide combiner
Implementation Method 3
Light is coupled into and out of waveguide combiners using surface relief gratings
Implementation Method 4
a pixelated phase modulator disposed on a second side of the waveguide combiner opposing the first side of the waveguide combiner
Data Source
AI summary
Embodiments described herein relate to waveguide combiners having arrangements for image uniformity. The waveguide combiners includes an input coupling grating (ICG) defined by a plurality of input structures, a pupil expansion grating (PEG) defined by a plurality of expansion structures, an output coupling grating (OCG) defined by a plurality of output structures The waveguide combiners includes at least one of a pixelated phase modulator is aligned with the PEG of the first side of the waveguide combiners, at least one of a Y expander and an X expander disposed on a second side of the waveguide combiners opposing the first side, or a pupil shifting mechanism operable to shift incident beams of light between a first position and a second position of the ICG.