Multispectral Imaging Device Using Quantum Well Segmentation
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Solution Overview
Problem
Existing multiple-quantum-well structures in multispectral thermal imaging devices are limited to very narrow wavelength ranges, making them ineffective for broad wavelength spectra imaging despite their high sensitivity.
Innovation Solution
A broadband active layer is introduced by alternating different quantum wells, and a matrix of individual detection pixels with specific diffraction gratings is used to create a multispectral imaging device capable of operating across a wide wavelength range, with one pixel lacking a diffraction grating for broadband response, and signal processing to enhance spectral coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard multiple-quantum-well structure with a single active layer is used, then high sensitivity is achieved within a narrow wavelength range, but the spectral bandwidth is limited to about 10%
Solution Approach 1:
The single active layer is segmented into multiple alternative active layers, each containing quantum wells with different well widths designed for specific wavelength subsets. By selectively activating different layers, the detector can operate across multiple wavelength ranges while maintaining high sensitivity for each subset.
Solution Approach 2:
The invention introduces dynamic wavelength selection capability by using alternative active layers that can be selectively activated. The system transitions from a static single-wavelength detection mode to a dynamic multi-wavelength mode, allowing the detector to adapt its spectral response based on operational requirements.
2Measurement precision
If diffraction gratings are added to each pixel for wavelength selection, then spectral selectivity is improved, but device complexity increases
Solution Approach 1:
Diffraction gratings are applied selectively only to specific pixels within the detector array that require wavelength selection, rather than uniformly to all pixels. This local application reduces overall device complexity while maintaining spectral selectivity where needed.
Solution Approach 2:
The alternative active layers serve multiple functions: they provide both the quantum well structure for high-sensitivity detection and the wavelength-selective filtering capability when combined with diffraction gratings. This multi-functionality reduces the need for separate components.
3Adaptability or versatility
If multiple alternative active layers with different quantum wells are used, then broadband spectral coverage is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The invention systematically varies the well width parameter across different alternative active layers to target different wavelength subsets. This parameter change approach allows for predictable spectral responses and simplifies the design process, making it easier to control manufacturing tolerances.
Solution Approach 2:
The detector uses composite structures combining multiple alternative active layers with different quantum well compositions and widths. These composite materials are designed to work together, with each layer contributing to a specific portion of the spectral range, thereby achieving broadband coverage while maintaining manufacturability.
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 solution enables multispectral imaging devices to operate effectively across a broad wavelength spectrum, maintaining high sensitivity and image resolution, and allowing for high frame rates with reduced spectral overlap and increased contrast.
Implementation Method 1
Rapid progress in epitaxial growth on GaAs-type substrates has resulted in the development of a new class of electromagnetic wave detectors using the absorption of radiation around a wavelength λ corresponding to the transition of electrons between various energy levels within the same energy band
Implementation Method 2
It has already been proposed to use coupling means of the diffraction grating type (cf. Goossen and Lyon, Appl. Phys. Lett. 47, 1257-1259 (1985)) for generating said perpendicular component by creating diffracted radiation
Data Source
AI summary
The invention relates to a multispectral imaging device comprising a multiple-quantum-well structure operating on inter-sub-band transitions by absorbing radiation at a wavelength λ lying within a set of wavelengths to which said structure is sensitive, said structure comprising a matrix of individual detection pixels, characterized in that the matrix is organized in subsets (Eij) of four individual detection pixels, a first individual detection pixel (Pλ1) comprising a first diffraction grating (Rλ1) sensitive to a first subset of wavelengths, a second individual detection pixel (Pλ2) comprising a second diffraction grating (Rλ2) sensitive to a second subset of wavelengths, a third individual detection pixel (Pλ3) comprising a third diffraction grating (Rλ3) sensitive to a third subset of wavelengths and a fourth individual detection pixel (PΔλ) not comprising a wavelength-selective diffraction grating, the first, second and third subsets of wavelengths belonging to the set of wavelengths to which said structure is sensitive.