Sensor Cap Coating for Infrared Cross-Sensitivity Reduction
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Solution Overview
Problem
Existing sensors for measuring fluid concentrations, such as carbon dioxide gas, face cross-sensitivity issues due to scattered light that can affect the accuracy of measurements, particularly because radiation passing through the gaps between filters can be detected by the sensing units.
Innovation Solution
A sensor apparatus with an absorption gap and a cap that is transparent to infrared radiation, featuring filters and pixel assemblages, where a coating on the cap prevents radiation from passing through non-filtered areas, ensuring each pixel assemblage detects only the radiation through its associated filter, thereby reducing cross-sensitivity and enhancing measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cap is made transparent to infrared radiation to allow radiation to reach pixel assemblages, then the sensor can detect infrared radiation, but scattered light can pass through non-filtered areas and cause cross-sensitivity
Solution Approach 1:
The cap is designed with non-uniform optical properties: transparent regions allow infrared radiation to pass through to pixel assemblages, while opaque coating regions block scattered light. This local differentiation of transparency resolves the contradiction by allowing detection where needed while preventing cross-sensitivity where not needed.
Solution Approach 2:
The cap surface is segmented into multiple functional zones: transparent areas aligned with filters and pixel assemblages, and opaque coated areas in between. This segmentation separates the useful radiation path from the harmful scattered light paths, maintaining both detection capability and measurement precision.
2Measurement precision
If filters are used to block specific wavelength regions, then cross-sensitivity is reduced, but radiation can still pass through gaps between filters and be detected
Solution Approach 1:
The harmful element (scattered light passing through filter gaps) is extracted and blocked by adding opaque coating regions on the cap between the filters. This removes the source of cross-sensitivity while preserving the filter function, ensuring that only radiation passing through the intended filter paths reaches the pixel assemblages.
3Measurement precision
If the cap is made opaque to block scattered light, then cross-sensitivity is prevented, but infrared radiation cannot reach the pixel assemblages
Solution Approach 1:
The cap exhibits spatially varying optical properties with transparent regions for radiation transmission and opaque coated regions for light blocking. This local quality differentiation resolves the contradiction by providing the necessary transparency for detection while introducing opacity precisely where scattered light would cause problems.
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 enhances the accuracy of fluid concentration measurements by preventing cross-sensitivity from scattered light, allowing for more precise detection of fluid concentrations based on infrared radiation intensity differences across the filters.
Implementation Method 1
infrared radiation that is propagated through an absorption gap filled with the gas to be measured is detected
Implementation Method 2
a concentration of the gas being measured on the basis of a difference in the intensities of the detected radiation
Implementation Method 3
a plurality of filters that are transparent to wavelength regions that differ at least in part from one another
Implementation Method 4
A coating made of a light-absorbing and/or light-reflecting material is configured at least locally on a part of the cap
Implementation Method 5
A coating made of a light-absorbing and/or light-reflecting material is configured at least locally on a part of the cap
Data Source
AI summary
A sensor apparatus having a sensor unit. The sensor unit including pixel assemblages on a substrate upper side of a substrate located on a lower side of the sensor unit; a cap, on the substrate upper side, which covers the pixel assemblages, a cavity being formed between the substrate upper side and the cap; a plurality of filters that are transparent to wavelength regions that differ from one another, exactly one pixel assemblage being associated with each filter; and the filters being on the cap so that the infrared radiation propagated through an absorption gap of the sensor apparatus and the upper side of the sensor unit is detectable, through the respective filter, by the pixel assemblage associated with the respective filter; and a coating made of a light-absorbing and/or light-reflecting material being configured at least locally on a part of the cap which is not covered by the filters.