Binary Multispectral Filter for Extended Near-Infrared Sensing
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Solution Overview
Problem
Conventional optical filters using silicon for high refractive index materials have limited spectral ranges, restricting the ability of sensor arrays to capture information across broader spectral ranges necessary for applications like gesture recognition, object recognition, and spectroscopic measurements.
Innovation Solution
A binary multispectral filter utilizing high refractive index materials such as hydrogenated silicon, silicon germanium, germanium, or hydrogenated germanium, which form alternating layers with low refractive index materials to extend the spectral range from approximately 1200 nm to 1800 nm, enabling near-infrared and short-wave infrared spectral range sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional silicon-based optical filters are used, then manufacturing simplicity is maintained, but spectral range coverage is limited
Solution Approach 1:
The patent employs composite material structures combining high refractive index materials (silicon germanium, germanium, or hydrogenated germanium) with low refractive index materials (silicon dioxide, silicon nitride, or aluminum oxide) to create a multispectral filter. This composite approach enables extended spectral range coverage from 1200 nm to 1900 nm while maintaining manufacturability through established deposition techniques.
Solution Approach 2:
The patent utilizes parameter changes in refractive index by selecting specific material combinations with distinct refractive index values (e.g., SiGe with n=3.9-4.0 and SiO2 with n=1.45) to design the filter layers. By optimizing the refractive index contrast and layer thicknesses, the filter achieves broad spectral coverage while controlling fabrication complexity.
2Adaptability or versatility
If broader spectral range materials are used, then spectral coverage is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes manufacturing ease by selecting materials with well-established deposition processes and controlled refractive indices. The high refractive index layers use silicon germanium, germanium, or hydrogenated germanium which can be deposited using standard semiconductor fabrication techniques, while low refractive index layers use silicon dioxide, silicon nitride, or aluminum oxide that are readily available materials with predictable fabrication characteristics.
Solution Approach 2:
The composite structure combines materials that are both manufacturable and functionally superior for extended spectral range. The specific material selections (SiGe, Ge, or Ge:H for high index; SiO2, SiN4, or Al2O3 for low index) represent a balance between achieving the required optical performance for 1200-1900 nm coverage and maintaining compatibility with existing manufacturing infrastructure.
3Adaptability or versatility
If alternating high and low refractive index layers are used, then spectral range is extended, but device complexity increases
Solution Approach 1:
The filter is segmented into multiple alternating layers of high and low refractive index materials, with each layer contributing to specific spectral filtering functions. This segmentation allows the broad spectral range from 1200 nm to 1900 nm to be achieved through a systematic arrangement of discrete functional elements rather than a single complex structure.
Solution Approach 2:
The alternating layer structure uses composite material pairs (e.g., SiGe/SiO2, Ge/SiN4, or Ge:H/Al2O3) where each material pair provides complementary optical properties. This composite approach manages structural complexity by using a repeating pattern of well-defined material interfaces that are straightforward to fabricate using standard semiconductor processing techniques.
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 binary multispectral filter enhances spectral range coverage, reduces spectral shift with increased angle of incidence, and improves sensing capabilities for biometric, health monitoring, and object identification systems by enabling a broader range of applications.
Implementation Method 1
a first mirror that includes a first subset of layers of a set of layers, and a second mirror that includes a second subset of layers of the set of layers
Implementation Method 2
The set of layers may include a plurality of high refractive index layers associated with a first refractive index and a plurality of low refractive index layers associated with a second refractive index that is less than the first refractive index
Data Source
AI summary
An optical filter may include a substrate, a first mirror that includes a first subset of layers of a set of layers, and a second mirror that includes a second subset of layers of the set of layers. The optical filter may include a spacer. The spacer may include a third subset of layers of the set of layers. The set of layers may include a plurality of high refractive index layers associated with a first refractive index and a plurality of low refractive index layers associated with a second refractive index that is less than the first refractive index. The optical filter may be associated with a spectral range from at least approximately 1200 nanometers (nm) to approximately 1900 nm.