Diffractive Image Combiner Layout for Exit Pupil Expansion
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Solution Overview
Problem
Existing augmented reality near-eye display technologies using diffractive optics suffer from a small exit pupil dimension, leading to user experience issues such as image loss due to eye movement, as the Eyebox is excessively small.
Innovation Solution
A diffractive image combiner utilizing multiple diffractive optical elements with aligned grating vectors to expand the exit pupil, ensuring parallel light rays are projected without crosstalk, thereby accommodating varying pupil distances and preventing image loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single diffractive optical element is used, then the device complexity is low, but the exit pupil dimension is small causing image loss
Solution Approach 1:
The patent divides the single diffractive optical element into multiple diffractive optical elements (first DOE and second DOE) with different grating vectors. Each element processes specific angular bands of light, collectively expanding the exit pupil dimension while maintaining manageable complexity through modular design.
Solution Approach 2:
The patent introduces a new dimension by adding multiple diffractive elements with different grating orientations (grating vectors). This dimensional expansion in the optical system allows simultaneous processing of multiple angular bands, thereby expanding the exit pupil without simply scaling up a single element.
2Adaptability or versatility
If multiple diffractive optical elements are used, then the exit pupil dimension is expanded, but the device complexity increases
Solution Approach 1:
The patent segments the angular bandwidth into multiple bands, with each diffractive element handling a specific segment. This segmentation allows the system to adapt to eye movements across different angular ranges while keeping each individual element relatively simple.
Solution Approach 2:
Each diffractive optical element is designed with specific grating vectors to handle different angular bands, giving the system multi-functionality. The combined system can adapt to various eye positions and movements, making the device versatile while maintaining reasonable complexity through specialized design.
3Area of stationary object
If the exit pupil dimension is small, then the device structure is simple, but user experience deteriorates due to image loss
Solution Approach 1:
By segmenting the angular spectrum into multiple bands handled by different diffractive elements, the patent creates a larger composite exit pupil. This ensures that light rays from various angles can reach the user's eye, maintaining image stability and preventing image loss during eye movements.
Solution Approach 2:
The patent effectively creates multiple copies of the optical function through different diffractive elements with different grating vectors. Each element copies the beam steering function for its specific angular band, collectively providing comprehensive coverage that maintains reliable image presentation.
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 expanded exit pupil accommodates user eye movement, improving user experience by preventing image loss and ensuring seamless virtual and real-world scene fusion.
Implementation Method 1
The first incidence point is used to convert an incident light ray that meets a Bragg condition into a first diffracted light ray
Implementation Method 2
The first incidence point is used to convert an incident light ray that meets a Bragg condition into a first diffracted light ray
Data Source
AI summary
A diffractive image combiner is provided, to increase an exit pupil dimension, thereby improving user experience. The diffractive image combiner includes a first diffractive optical element (DOE) and a second DOE. The first DOE is parallel to the second DOE. A grating vector of a first incidence point in the first DOE is the same as a grating vector of a second incidence point in the second DOE. The first incidence point is used to convert an incident light ray that meets a Bragg condition into a first diffracted light ray and a first transmitted light ray. The first transmitted light ray is incident to the second incidence point. The second incidence point is used to convert the first transmitted light ray into a second diffracted light ray.