Optical Light Guide with Diffractive Expansion for Dark-Band Reduction
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Solution Overview
Problem
Existing optical apparatuses, such as exit pupil expanders, often result in non-uniform light output, leading to visible dark bands and uneven brightness in displays like near-eye displays and head-up displays.
Innovation Solution
The apparatus incorporates a light guiding means with multiple diffractive elements, including first and second in-coupling diffractive means and expanding diffractive means, arranged to guide and expand light beams uniformly across a surface, using symmetrical and perpendicular gratings to ensure even distribution of light across the exit pupil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional exit pupil expanders are used, then light expansion is achieved, but uniform light output deteriorates resulting in visible dark bands and uneven brightness
Solution Approach 1:
The light guiding means is divided into multiple functional zones: first in-coupling diffractive means, first expanding diffractive means, second expanding diffractive means, second in-coupling diffractive means, and out-coupling diffractive means. Each zone performs a specific function in the light manipulation sequence, with the out-coupling means having distinct first and second regions that correspond to different light paths, thereby achieving uniform light distribution and eliminating dark bands
Solution Approach 2:
The out-coupling diffractive means has different local properties in different regions - the first region corresponds to light from the first expanding means while the second region corresponds to light from the second expanding means. This local differentiation in the out-coupling structure ensures that each region properly handles its corresponding light path, resulting in uniform overall output without dark bands
2Illumination intensity
If multiple diffractive elements are added to improve light uniformity, then light output uniformity improves, but device complexity increases
Solution Approach 1:
Multiple diffractive elements (first in-coupling, first expanding, second expanding, second in-coupling, and out-coupling means) are merged into a single integrated light guiding means. This consolidation achieves uniform light output through coordinated interaction of all elements while maintaining a compact, unified structure rather than separate components, thus improving uniformity without proportionally increasing overall device complexity
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 provides a more uniform and efficient light output, reducing dark bands and enhancing the overall brightness and clarity of the displayed images.
Implementation Method 1
first in-coupling diffractive means configured to in-couple one or more input beams of light into the light guiding means, first expanding diffractive means and second expanding diffractive means configured to expand the one or more input beams of light
Implementation Method 2
The light guiding means may comprise a stack of layers wherein 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
Data Source
Figure 1A~1F
Figure 2A~2F
Figure 3A~3C
AI summary
Examples of the disclosure relate to optical apparatus. The apparatus comprises a light guiding means. The light guiding means comprises at least; first in-coupling diffractive means, first expanding diffractive means and second expanding diffractive means, second in-coupling diffractive means, and one or more out-coupling diffractive means. The first in-coupling diffractive means are configured to in-couple one or more input beams of light into the light guiding means. The first expanding diffractive means and second expanding diffractive means are configured to expand the one or more input beams of light wherein the first expanding diffractive means is provided on a first side of the first in-coupling diffractive means and the second expanding diffractive means is provided on a second side of the first in-coupling diffractive means. The second in-coupling diffractive means are configured to in-couple one or more input beams of light into the light guiding means. The one or more out-coupling diffractive means are configured to out-couple light from the first expanding diffractive means, the second expanding diffractive means and the second in-coupling diffractive means.