Multispectral Optical Filter with Tuned Resonant Cavities
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Solution Overview
Problem
Existing multispectral sensors face challenges in achieving a wide spectral band and high resolution due to limitations in compact optical filters.
Innovation Solution
The optical filter is designed with resonant cavities of varying thicknesses and diffraction gratings with different filling factors, each cavity comprising a first transparent layer interposed between mirror layers, allowing for the transmission of incident radiation in different wavelength ranges and enhancing spectral and spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single optical filter is used to transmit multiple wavelength ranges, then the device compactness is improved, but the spectral resolution and spectral band width deteriorate
Solution Approach 1:
The optical filter is segmented into multiple resonant cavities, each with a specific thickness designed to transmit a particular wavelength range. Each cavity acts as an independent spectral filter, allowing the combined structure to achieve high spectral resolution while maintaining a compact single-filter design.
Solution Approach 2:
Different regions of the optical filter have different local properties through varying cavity thicknesses. Thinner cavities transmit shorter wavelengths while thicker cavities transmit longer wavelengths, enabling the filter to cover a broad spectral band with high resolution across different wavelength ranges simultaneously.
2Adaptability or versatility
If resonant cavities of different thicknesses are used, then the spectral band width is improved, but the manufacturing complexity worsens
Solution Approach 1:
The filter is divided into discrete resonant cavities with different thicknesses, where each cavity targets a specific wavelength range. This segmentation allows for systematic design and manufacturing, with each cavity being an identical structure but with controlled thickness variations to achieve different spectral responses.
Solution Approach 2:
The key parameter that varies between cavities is the thickness of the resonant cavity structure. By controlling this single parameter during manufacturing, the filter achieves broad spectral coverage without requiring complex structural variations, simplifying the overall manufacturing process while expanding spectral capabilities.
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 multispectral sensors to access a wider spectral band and higher resolution than existing technologies, while maintaining compactness, by combining resonant cavities of different thicknesses with diffraction gratings of varying filling factors.
Implementation Method 1
for each pixel, a resonant cavity comprising a first transparent layer, interposed between second and third mirror layers
Implementation Method 2
resonant cavity comprising a first transparent layer, interposed between second and third mirror layers
Implementation Method 3
a diffraction grating formed in the first layer
Data Source
AI summary
The present description concerns an optical filter intended to be arranged in front of an image sensor comprising a plurality of pixels, the filter comprising, for each pixel, a resonant cavity comprising a first transparent layer, interposed between second and third mirror layers, and a diffraction grating formed in the first layer, wherein at least one of the cavities has a different thickness than another cavity.