Stress-Balanced Optical Interference Filter for Low Angle Shift
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Solution Overview
Problem
Conventional optical filters suffer from complex layer formation, defects, bowing, reduced durability, and increased angle shift with changes in incidence angle, leading to degraded performance and handling issues.
Innovation Solution
An optical interference filter with alternating layers of scandium, aluminum, and nitrogen, and silicon and oxygen, which balances tensile and compressive stresses to minimize bowing and angle shift, enhancing transmittance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical filters use complex layer formation with multiple materials, then filtering performance is achieved, but manufacturing complexity and defect formation increase
Solution Approach 1:
The patent extracts and eliminates one material layer from the conventional three-material stack, reducing the layer structure from three alternating materials to two. This simplification maintains the optical filtering function while reducing manufacturing complexity and defect formation opportunities.
Solution Approach 2:
The patent employs composite material design by combining specific materials (scandium aluminum nitride and silicon dioxide) with complementary properties - one providing tensile stress and the other compressive stress - to create a balanced multilayer structure that achieves both optical performance and mechanical stability.
2Ease of manufacture
If conventional optical filters use compressive stress layers, then layer formation is achieved, but bowing and fragility increase
Solution Approach 1:
The patent applies counterweight principle by introducing tensile stress layers to balance the compressive stress layers within the filter structure. This stress compensation prevents net bowing and reduces fragility, making the filter more durable while maintaining manufacturability.
Solution Approach 2:
The patent changes the stress state parameter of the layers by selecting materials with opposite stress characteristics (tensile vs. compressive) and adjusting their thickness ratios to achieve stress balance, thereby transforming the mechanical properties of the filter.
3Productivity
If conventional optical filters use standard layer structures, then manufacturing is achieved, but angle shift with incidence changes increases
Solution Approach 1:
The patent changes the optical parameters of the layer structure by using materials with specific refractive indices and adjusting the thickness ratios of alternating layers. This optimization reduces the angle shift effect while maintaining standard manufacturing 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
The filter achieves high transmittance (>85%) with minimal angle shift (<1% at 30° incidence), improved manufacturability, and increased durability, reducing defects and handling difficulties.
Implementation Method 1
An optical interference filter includes one or more sets of layers that are disposed on a substrate
Data Source
AI summary
An optical interference filter includes a substrate and one or more sets of layers that are disposed on the substrate. Each set of layers includes a first layer that comprises at least scandium, aluminum, and nitrogen, and a second layer that comprises at least silicon and oxygen. The first layer may comprise at least one of a scandium aluminum nitride (ScAlN) material or a scandium aluminum nitrogen oxide (ScAlNO) material. The second layer may comprise a hydrogenated silicon (Si:H) material. An absolute value of a net stress of the one or more sets of layers may be less than or equal to 50 megapascals.