Asymmetric Filter Array for Hyperspectral Imaging
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Solution Overview
Problem
Existing hyperspectral camera systems face challenges in maintaining high spectral resolution and detection light intensity due to changes in transmission spectra between vertical and oblique light incidence, and the use of Fabry-Perot resonators with high reflectance layers can lead to decreased transmittance between wavelength peaks.
Innovation Solution
A filter array is designed with optical filters having an interference layer with opposite surfaces of different reflectance, and a reflective layer only on one surface, which helps maintain spectral resolution and light intensity by minimizing changes in transmission spectra with varying light incidence angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Fabry-Perot resonator with high reflectance layers is used to achieve high spectral resolution, then the spectral resolution is improved, but the transmittance between wavelength peaks decreases
Solution Approach 1:
The patent applies asymmetry by providing a reflective layer only on the first surface of the interference layer but not on the second surface. This asymmetric configuration creates different reflectance characteristics for light incident from different directions, allowing the filter to maintain high spectral resolution through the interference layer's wavelength-selective properties while avoiding excessive light loss that would occur with symmetric high-reflectance layers on both surfaces.
Solution Approach 2:
The patent applies local quality by making the reflectance properties location-dependent within the optical filter structure. The first surface has a reflective layer providing high reflectance for wavelength-selective filtering, while the second surface has no reflective layer to minimize light loss. This localized differentiation of optical properties allows the filter to achieve both high spectral resolution and adequate light transmission.
2Measurement precision
If optical filters with high reflectance layers are used to achieve narrow bandwidth filtering, then the spectral resolution is improved, but the transmission spectrum changes significantly with oblique light incidence
Solution Approach 1:
The asymmetric structure with a reflective layer on only one surface creates different optical path lengths and interference conditions for oblique incident light compared to symmetric structures. This asymmetry helps stabilize the transmission spectrum by reducing the sensitivity to incidence angle changes, as the single reflective interface provides more consistent phase relationships for varying angles of incidence.
3Measurement precision
If conventional optical filter structures are used to maintain spectral resolution, then the spectral resolution is preserved, but the detection light intensity decreases due to multiple reflective interfaces
Solution Approach 1:
The patent applies the extraction principle by removing the reflective layer from the second surface of the interference layer. This extraction eliminates the additional light loss that would occur at a second reflective interface, allowing more light to transmit through the filter while the first surface's reflective layer maintains the necessary wavelength-selective filtering for spectral resolution.
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 proposed filter array enhances the spectral resolution and detection light intensity of hyperspectral cameras by stabilizing the transmission spectrum across different light incidence angles, thereby improving image quality and data accuracy.
Implementation Method 1
at least one optical filter of the optical filters includes an interference layer having a first surface and a second surface opposite the first surface, and a reflective layer provided on the first surface
Implementation Method 2
a reflective layer provided on the first surface. A transmission spectrum of the at least one optical filter has maximum values
Data Source
AI summary
A filter array includes optical filters that are disposed in a two-dimensional plane. At least one optical filter of the optical filters includes an interference layer having a first surface and a second surface opposite the first surface, and a reflective layer provided on the first surface. A transmission spectrum of the at least one optical filter has maximum values. The reflective layer is not provided on the second surface.