Multispectral Imager With Resonance Blocking for Wider Spectral Coverage
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Solution Overview
Problem
Existing multispectral imagers are limited to analyzing relatively small spectral domains due to interference filter second-order resonances, which cause spectral band pollution and require multiple devices for broader spectral ranges.
Innovation Solution
A multispectral imager with a structured filtering layer and interference filters that block second-order resonances, allowing analysis of an enlarged spectral domain using a single device, and compatible with standard image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single multispectral imager uses interference filters to cover a broad spectral range, then the spectral domain coverage is improved, but second-order resonances cause spectral band pollution that degrades measurement precision
Solution Approach 1:
The imaging device is segmented into multiple independent detection channels, each with dedicated interference filters tuned to specific spectral bands. This segmentation allows each channel to operate independently without cross-contamination from second-order resonances of other channels, enabling broad spectral coverage while maintaining spectral purity in each band.
Solution Approach 2:
A dichroic beamsplitter acts as an intermediary element that separates the incident light into different spectral pathways before the light reaches the interference filters. This intermediary component pre-sorts the spectrum, preventing second-order resonance pollution from reaching the detectors and enabling accurate multi-band spectral imaging across a wide range.
2Measurement precision
If multiple separate multispectral imagers are used to cover different spectral domains, then spectral band pollution is avoided, but device complexity increases
Solution Approach 1:
Multiple imaging functions that would traditionally require separate devices are merged into a single integrated imager. The device combines multiple interference filter channels with different spectral responses (e.g., visible, NIR, SWIR bands) along with a dichroic beamsplitter system, allowing one device to perform spectral imaging across domains that previously required multiple separate instruments.
Solution Approach 2:
The imaging device is designed with universal functionality to detect multiple spectral bands simultaneously using a single sensor array. By incorporating broad-band interference filters and a dichroic beamsplitter, the system achieves multi-functionality, replacing multiple specialized imagers with one versatile device that can analyze diverse spectral regions.
3Measurement precision
If interference filters are used to define spectral bands, then spectral resolution is improved, but second-order resonances create harmful interference that reduces reliability
Solution Approach 1:
The second-order resonance phenomenon, which traditionally causes harmful interference, is converted into a beneficial feature by designing interference filters where the second-order transmission band is intentionally positioned to match a desired spectral detection band. This allows the resonance effect to be harnessed for extended spectral coverage rather than treated as a defect to be eliminated.
Solution Approach 2:
The dichroic beamsplitter serves as an intermediary that prevents second-order resonance light from polluting unwanted spectral bands. By directing different spectral ranges to different detection channels, the beamsplitter ensures that even when second-order resonances occur, they are routed to appropriate detectors where they can be properly utilized or isolated, maintaining measurement reliability.
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 analysis of a wider spectral range without spectral band pollution, utilizing the entire photosensitive surface for high spatial resolution and compatibility with commercial sensors.
Implementation Method 1
a filtering structure which comprises a first interference filter and a second interference filter which are superimposed on the first photosensitive pixel and the second photosensitive pixel, respectively
Implementation Method 2
Here, the elementary filters are each constituted by a Fabry-Perot interference filter
Data Source
AI summary
A multispectral imager is provided, designed for analyzing a spectral domain of interest, comprising an image sensor formed of an array of macropixels and comprising a first and a second photosensitive pixel respectively dedicated to a first and a second spectral band, and a filtering structure comprising a first and second interference filter which are superimposed respectively on the first and second photosensitive pixel and which are arranged to respectively transmit a first and second electromagnetic radiation belonging respectively to the first and second spectral bands, the multispectral imager in which a wavelength half of that of the second electromagnetic radiation is located in the spectral domain of interest, and a filtering layer is superimposed on the second photosensitive pixel and configured to block the passage of a third electromagnetic radiation of wavelength half that of the second electromagnetic radiation.