LCOS Panel Diffraction Reduction via Dielectric Index Matching
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Solution Overview
Problem
Liquid crystal on silicon (LCOS) panels used in near eye displays for 3D augmented and virtual reality suffer from light diffraction due to their periodic metal electrode structure, leading to reduced image intensity, and existing high-reflection coatings compromise the contrast ratio when attempting to mitigate diffraction.
Innovation Solution
The use of high refractive index dielectric materials to fill the gaps between metal electrodes, or surrounding metal pillars with dielectric material, to minimize diffraction while maintaining the same thickness of the oxide layer, thus preserving the electric field and contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a high-reflection coating is applied to cover metal electrodes and gaps, then diffraction is reduced, but contrast ratio decreases
Solution Approach 1:
The patent applies different materials with different refractive indices to different locations: high refractive index dielectric material (n>2.0) in gaps between electrodes, and standard oxide layer (n≈1.46) on metal electrodes. This local differentiation reduces diffraction at gaps while preserving the electric field and contrast ratio on the electrode surfaces.
Solution Approach 2:
The patent changes the refractive index parameter of the dielectric material in the gaps between electrodes to be higher than 2.0, which optimizes the reduction of diffraction. This parameter change allows the gaps to better match the optical properties of the metal electrodes, reducing the diffraction effect without requiring a thick high-reflection coating that would compromise contrast ratio.
2Object-affected harmful factors
If oxide layer thickness is increased to reduce diffraction, then diffraction is reduced, but electric field generation is affected
Solution Approach 1:
The patent maintains the oxide layer thickness on metal electrodes at the optimal value for electric field generation, while only filling the gaps between electrodes with high refractive index dielectric material. This localized approach reduces diffraction without increasing the oxide layer thickness on the electrodes themselves, thus preserving the electric field generation.
3Object-affected harmful factors
If high refractive index dielectric material is used to fill gaps, then diffraction is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the dielectric layer into two functional parts: a first dielectric layer (oxide) formed on the metal electrodes, and a second dielectric layer (high refractive index material) filling the gaps between electrodes. This segmentation allows each layer to be optimized independently and simplifies the manufacturing process by using standard deposition techniques for each material layer.
Solution Approach 2:
The high refractive index dielectric material serves multiple functions: it fills the gaps between electrodes, reduces diffraction, and maintains the overall planarity of the surface. This multi-functionality reduces the need for additional specialized components or processes.
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 approach significantly reduces diffraction in LCOS panels without sacrificing contrast ratio, enhancing the intensity of the image seen by the eye and improving the diffraction ratio, resulting in a more effective near eye display technology.
Implementation Method 1
Some of light may be diffracted by the LCOS panel periodical structure, and thus the intensity of the image seen by the eye decreases
Implementation Method 2
The high refractive index dielectric material has a refractive index higher than 2.0, and the refractive index of the oxide layer is about 1.46
Data Source
AI summary
A liquid crystal on silicon (LCOS) panel comprises: a silicon substrate having silicon circuit within the silicon substrate; a plurality of metal electrodes disposed on the silicon substrate, where the plurality of metal electrodes are periodically formed on the silicon substrate; a dielectric material disposed in and filling gaps between adjacent metal electrodes; and an oxide layer disposed on the plurality of metal electrodes and the dielectric material in the gaps between adjacent metal electrodes; where the refractive index of the dielectric material is higher than the refractive index of the oxide layer.