Multispectral Photodetector Layout With Spaced Filters for Low Crosstalk
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Solution Overview
Problem
Existing multispectral detection devices are complex and costly to produce due to the need for multiple photodetectors and filters to capture different spectral bands, which complicates manufacturing and integration, especially for compact and high-performance devices.
Innovation Solution
A multispectral detection device comprising a first and second photodetector sensitive to overlapping wavelength ranges, with a first filter blocking the second wavelength range and a second filter positioned at a distance, configured to pass both wavelength ranges, allowing for the use of identical photodetectors and simplifying the filtering system by separating the filters to reduce thickness and thermomechanical constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple photodetectors with different semiconductor materials are used to detect different spectral bands, then spectral detection capability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses identical photodetectors that can detect multiple spectral bands (first and second wavelength ranges) simultaneously. By making the photodetectors universal and capable of detecting both spectral bands, the system eliminates the need for different photodetector types with different semiconductor materials, thereby reducing device complexity while maintaining spectral detection capability
Solution Approach 2:
The patent segments the spectral filtering function from the photodetector detection function. Instead of having photodetectors with different materials detect different bands, the system uses identical photodetectors with broadband sensitivity and places filters in front of them to select specific wavelength ranges. This segmentation allows the photodetectors to be simplified while the filtering handles spectral differentiation
2Adaptability or versatility
If filters are placed directly on photodetectors to specialize them for specific spectral bands, then spectral selectivity is improved, but manufacturing complexity and integration difficulty increase
Solution Approach 1:
The patent positions the second filter at a distance from the photodetector array, separate from the first filters that are directly on the photodetectors. This spatial separation in the optical path allows for easier manufacturing and alignment, as the filters are not all constrained to be in direct contact with the photodetector surfaces, reducing integration complexity
3Measurement precision
If filters are placed in contact with photodetectors to block unwanted wavelength ranges, then spectral filtering performance is improved, but thermomechanical stresses and device reliability issues increase
Solution Approach 1:
The patent positions the second filter at a distance from the photodetector array, separated by a non-contact space. This spatial separation eliminates direct mechanical contact between the filters and photodetectors, thereby eliminating thermomechanical stresses that would arise from thermal expansion mismatches while maintaining the spectral filtering performance through the optical path arrangement
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 configuration enables the production of a more compact, easier-to-manufacture multispectral detection device that effectively filters radiation, reducing crosstalk and thermomechanical stresses while maintaining high performance.
Implementation Method 1
a first filter configured to allow the first wavelength range to pass through and to block the second wavelength range, the first filter covering the first photodetector and leaving the second photodetector exposed
Implementation Method 2
a second filter disposed at a distance from the first and second photodetectors and at a distance from the first filter, the second filter being configured to allow the first wavelength range and the second wavelength range to pass through, the second filter being configured to block a wavelength greater than the longest of the wavelengths among the first and second wavelength ranges and/or to block a wavelength shorter than the shortest of the wavelengths among the first and second wavelength ranges
Implementation Method 3
a first photodetector and a second photodetector, each sensitive to a first wavelength range and a second wavelength range different from the first wavelength range, the first photodetector delivering a first signal representative of the received radiation and the second photodetector delivering a second signal representative of the received radiation
Data Source
Figure 1
Figure 2
Figure 3a~3f
AI summary
The detection device comprises first and second photodetectors (1a, 1b) each sensitive to two different wavelength ranges. The detection device comprises a first filter (4a) configured to allow the passage of the first wavelength range and to block the second wavelength range. The first filter covers the first photodetector (1a) and leaves the second photodetector (1b) uncovered. The detection device comprises a second filter (4b) arranged spaced apart from the first and second photodetectors (1a, 1b) and spaced apart from the first filter (4a). The second filter (4b) is configured to allow the passage of the first and second wavelength ranges. A processing circuit (5) is configured to receive electrical signals coming from the first and second photodetectors (1a, 1b) and to provide a piece of information relating to the radiation of the second range of wavelengths by comparing the first signal with the second signal (7a).