Optical Filter Structure for Visible and Infrared Spectral Separation
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Solution Overview
Problem
Current optical filtering structures require multiple dielectric layers and complex processes to achieve simultaneous detection or emission of visible and infrared spectral bands, leading to increased complexity and signal degradation due to the need for separate sensors and filters.
Innovation Solution
A filtering structure using a stack of dielectric layers with alternating refractive indices and metal layers, allowing for the integration of visible-pass and infrared-cut filters, and infrared-pass and visible-cut filters on a single detection or emission matrix with fewer than 10 dielectric layers, eliminating the need for a black resin and simplifying production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple dielectric layers are used to achieve simultaneous visible and infrared filtering, then spectral selectivity is improved, but device complexity increases
Solution Approach 1:
The patent combines visible-pass/infrared-cut filtering and infrared-pass/visible-cut filtering into a single integrated optical filter structure. This merging eliminates the need for separate filters and reduces the overall number of dielectric layers required, while maintaining the spectral selectivity of both filtering functions through a unified multilayer design.
Solution Approach 2:
The optical filter structure is designed to perform multiple filtering functions simultaneously - it provides both visible-pass/infrared-cut filtering and infrared-pass/visible-cut filtering within a single device. This multi-functionality allows the filter to serve multiple purposes in photodetector arrays, reducing system complexity while maintaining spectral selectivity.
2Measurement precision
If separate sensors are used for visible and infrared detection, then spectral detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges visible and infrared detection capabilities into a single photodetector array by using complementary optical filters that direct different spectral bands to different pixel types within the same sensor. This approach maintains spectral detection accuracy while eliminating the need for separate visible and infrared sensors, thereby reducing device complexity.
Solution Approach 2:
The patent segments the photodetector array into different pixel types (e.g., visible-sensitive pixels and infrared-sensitive pixels) and uses optical filters to direct appropriate spectral bands to each pixel type. This segmentation allows simultaneous visible and infrared detection within a single sensor, maintaining detection accuracy while reducing overall device complexity.
3Manufacturing precision
If black resin is used for infrared blocking, then infrared cutoff is improved, but visible light absorption increases
Solution Approach 1:
The patent applies different filtering properties to different regions or spectral bands within the optical filter structure. The filter is designed to provide strong infrared cutoff while maintaining high visible light transmission through carefully selected dielectric layer materials and thicknesses, achieving local optimization of spectral selectivity without unnecessary visible light absorption.
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
Enables efficient detection and emission of multiple spectral bands on a single matrix, reducing production complexity and cost, while maintaining high signal quality by minimizing absorption and improving spectral selectivity.
Implementation Method 1
a first filter making it possible, facing a first set of pixels, to let a first spectral band pass and cut a second spectral band, and a second filter making it possible, facing a second set of pixels, to let the second spectral band pass and cut the first spectral band
Implementation Method 2
stack of dielectric layers with alternating refractive indices
Implementation Method 3
A filtering structure using a stack of dielectric layers with alternating refractive indices and metal layers
Data Source
Figure 1~2
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Figure 5~6
AI summary
The structure (111) has a stack of layers forming a visible pass and infrared cut off filter (112) and an infrared pass and visible cut off filter to pass wavelengths of spectral bands, and comprising silicon nitride layers (116, 120, 124, 128, 132) and silicon dioxide layer (122) common to the filters. A copper layer (118) is arranged common to the filters, and another copper layer (126) is arranged only in one of the filters. The silicon dioxide layer includes the filters having different thicknesses, where the nitride layer is arranged only in one of the filters. Independent claims are also included for the following: (1) a photodetector and/or photoemitter device (2) a method for forming an optical filtering structure.