Diffractive Light Guide Layout for Uniform Exit Pupil Expansion
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Solution Overview
Problem
Existing optical apparatuses, such as exit pupil expanders, often result in non-uniform output due to dark bands and uneven brightness distribution, which can be exacerbated by angled input beams.
Innovation Solution
The apparatus employs a light guiding means with multiple diffractive elements, including first and second in-coupling diffractive means and expanding diffractive means, arranged to distribute light evenly across different regions, utilizing symmetrical and perpendicular gratings to enhance uniformity and reduce dark bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional exit pupil expanders are used, then the exit pupil size is expanded, but the output becomes non-uniform with dark bands and uneven brightness distribution
Solution Approach 1:
The patent divides the light guiding means into multiple segments with different diffractive elements (first in-coupling diffractive means, second in-coupling diffractive means, first expanding diffractive means, second expanding diffractive means, and out-coupling diffractive means) arranged at different positions and orientations. Each segment handles specific light paths and contributes to uniformizing the overall output by addressing different regions of the exit pupil independently.
Solution Approach 2:
The patent employs asymmetric arrangement of diffractive elements with different orientations and positions. The first and second in-coupling diffractive means are oriented at different angles, and the expanding diffractive means are positioned asymmetrically to compensate for dark bands in specific regions. This asymmetric design allows targeted correction of non-uniformity patterns that would result from symmetric arrangements.
2Adaptability or versatility
If angled input beams are used, then the device can accommodate oblique light sources, but the dark bands and non-uniformity are exacerbated
Solution Approach 1:
The patent designs the diffractive elements with specific angular orientations that are optimized to handle angled input beams. The first in-coupling diffractive means and second in-coupling diffractive means are oriented at different angles relative to the light guiding means surface, allowing the system to dynamically adapt to various input beam angles while maintaining uniform output. This angular optimization ensures that oblique inputs do not create concentrated dark bands.
3Illumination intensity
If multiple diffractive elements are added to improve uniformity, then the brightness distribution becomes more uniform, but the device complexity increases
Solution Approach 1:
The patent merges multiple diffractive functions into a single integrated light guiding means structure. The first in-coupling diffractive means, second in-coupling diffractive means, first expanding diffractive means, second expanding diffractive means, and out-coupling diffractive means are all integrated into one component rather than being separate discrete elements. This merging reduces assembly complexity and spatial requirements while maintaining the uniformizing effect of multiple diffractive stages.
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 a more uniform output by distributing light evenly, reducing dark bands and enhancing brightness consistency, even with angled input beams, thereby improving the display quality.
Implementation Method 1
first in-coupling diffractive means configured to in-couple one or more input beams of light into the light guiding means
Implementation Method 2
first expanding diffractive means and second expanding diffractive means configured to expand the one or more input beams of light
Implementation Method 3
respective layers within the stack are arranged to enable beams of light comprising at least light having a first wavelength and light having a second wavelength to be guided through the light guiding means via internal reflections
Implementation Method 4
one or more out-coupling diffractive means configured to out-couple light from the first expanding diffractive means, the second expanding diffractive means and the second in-coupling diffractive means
Data Source
AI summary
An optical apparatus includes a light guide, which includes at least a first diffractive in-coupler, a first diffractive expander and a second diffractive expander, a second diffractive in-coupler, and one or more diffractive out-couplers. The first diffractive in-coupler is configured to in-couple input beams of light into the light guide. The first and second diffractive expanders are configured to expand the input beams of light wherein the first diffractive expander is provided on a first side of the first diffractive in-coupler and the second diffractive expander is provided on a second side of the first diffractive in-coupler. The second diffractive in-coupler is configured to in-couple input beams of light into the light guide. The diffractive out-couplers are configured to out-couple light from the first and second diffractive expanders and the second diffractive in-coupler.