Inverse Diffractive Substrates for Uniform Exit Pupil Expansion
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Solution Overview
Problem
Existing optical apparatuses, such as exit pupil expanders, face challenges in improving efficiency and uniformity, particularly in augmented reality and heads-up display systems, where existing solutions do not adequately address chromatic dispersion and nonuniformity issues.
Innovation Solution
The use of stacked substrates with inverse diffractive optical elements, where each substrate has incoupling and outcoupling elements configured to operate in different spectral ranges, and the elements are inversely designed to enhance light coupling and expansion, allowing for improved efficiency and uniformity of exit pupil expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional optical apparatuses are used for exit pupil expansion, then the basic function is achieved, but light coupling efficiency and uniformity are insufficient
Solution Approach 1:
The optical apparatus is divided into multiple substrates (first substrate, second substrate, third substrate) with each containing specific diffractive optical elements. This segmentation allows independent optimization of light coupling and uniformity functions across different layers, resolving the contradiction between coupling efficiency and output uniformity.
Solution Approach 2:
The patent employs inverse diffractive optical elements where the diffractive pattern of one element is the inverse of another (e.g., protrusions become recesses). This inversion principle enables complementary light manipulation that simultaneously improves coupling efficiency and uniformity by compensating for nonuniformities in the light path.
2Productivity
If multiple separate optical components are used to improve efficiency and uniformity, then performance improves, but device complexity increases
Solution Approach 1:
Multiple diffractive optical elements are integrated onto a single substrate, combining multiple functions (light coupling, light expansion, uniformity compensation) into one component. This merging reduces the overall number of separate optical components while maintaining improved efficiency and uniformity performance.
Solution Approach 2:
The substrates are designed to perform multiple functions simultaneously - coupling light into the substrate, expanding the exit pupil, and compensating for nonuniformities all within the same optical element structure. This multi-functionality reduces device complexity by eliminating the need for separate dedicated components for each function.
3Manufacturing precision
If tight manufacturing tolerances are required for precise diffractive patterns, then optical performance improves, but manufacturing cost increases
Solution Approach 1:
The patent uses master moulds to create diffractive optical elements, where the master mould is replicated to produce multiple substrates. This copying approach ensures consistent precision across all elements while simplifying manufacturing compared to individual precision fabrication, as the master mould can be manufactured once and then replicated. The inverse elements are created by copying the master mould with inverted geometry.
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
This configuration enhances light utilization by recycling light through additional substrates, compensates for nonuniformities, and reduces manufacturing tolerances while maintaining high quality, thus improving the efficiency and uniformity of exit pupil expansion.
Implementation Method 1
a first substrate comprising a first incoupling diffractive optical element configured to couple light into the first substrate, and a first outcoupling diffractive optical element configured to output, from the first substrate, light that has been coupled into the first substrate
Implementation Method 2
the apparatus comprises polarization rotation means and/or wavelength dependent filtering means between the first and second incoupling diffractive optical elements
Implementation Method 3
the apparatus comprises polarization rotation means and/or wavelength dependent filtering means between the first and second incoupling diffractive optical elements
Data Source
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AI summary
An apparatus comprising: a first substrate comprising a first incoupling diffractive optical element configured to couple light into the first substrate, and a first outcoupling diffractive optical element configured to output, from the first substrate, light that has been coupled into the first substrate; and a second substrate comprising a second incoupling diffractive optical element configured to couple light into the second substrate, and a second outcoupling diffractive optical element configured to output, from the second substrate, light that has been coupled into the second substrate; wherein the first and second incoupling diffractive optical elements are substantially inverse of each other and the first and second outcoupling diffractive optical elements are substantially inverse of each other.