NIRS Sensor EMI Shielding for Signal Quality
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Solution Overview
Problem
Near-infrared spectroscopy (NIRS) sensors face challenges in accurately determining tissue oxygenation levels due to signal interference from ambient light and electromagnetic interference (EMI), and they are often costly and difficult to manufacture, with extracerebral tissue attenuation complicating cerebral oxygenation monitoring.
Innovation Solution
A NIRS sensor assembly with a pad, light sources, light detectors, and EMI shielding, featuring independent detector housings that reduce noise and enhance manufacturing ease, flexibility, and cost-effectiveness, while maintaining accurate light source-detector separation distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NIRS sensors are used without EMI shielding, then the device structure remains simple and manufacturing cost is lower, but electromagnetic interference noise degrades signal quality and measurement accuracy
Solution Approach 1:
The patent introduces EMI shielding as an intermediary component between the light detector and the external electromagnetic environment. The shielding acts as a mediator that blocks harmful EMI while allowing the desired near-infrared light signals to pass through to the detector, thereby improving signal quality without fundamentally changing the core NIRS measurement function.
Solution Approach 2:
The patent employs inexpensive EMI shielding materials such as conductive paint, metallic foil, or conductive fabric that can be easily applied to the sensor housing or detector packaging. These shielding layers are simple to implement and can be manufactured at low cost, providing effective EMI protection without significantly increasing device complexity or manufacturing expense.
2Measurement precision
If EMI shielding is added to the sensor assembly, then electromagnetic interference noise is reduced and signal quality improves, but manufacturing cost and production complexity increase
Solution Approach 1:
The patent utilizes thin film EMI shielding materials such as conductive coatings, metallic foils, or conductive fabrics that can be easily applied to the sensor housing or detector packaging. These flexible thin films provide effective EMI protection while being simple to manufacture and integrate into the existing sensor assembly process, minimizing increases in manufacturing cost and complexity.
Solution Approach 2:
The patent explores different EMI shielding material options with varying levels of conductivity, thickness, and frequency response characteristics. By selecting shielding materials and configurations that provide adequate protection for the specific near-infrared wavelength range used, the design achieves effective EMI noise reduction while optimizing manufacturing cost and ease of production.
3Measurement precision
If complex sensor assemblies with integrated EMI shielding are manufactured, then measurement accuracy improves, but production time and manufacturing complexity increase
Solution Approach 1:
The patent structures the EMI shielding as a separate, modular component that can be independently manufactured and then integrated with the NIRS sensor assembly. This segmentation allows the shielding to be produced using simple processes and then attached to the sensor housing or detector package in a straightforward assembly step, minimizing increases in production time while ensuring proper EMI protection.
Solution Approach 2:
The EMI shielding serves as an intermediary component that can be independently sourced and integrated into the final sensor assembly. By treating the shielding as a separate module rather than an integrated feature requiring complex co-manufacturing with the optical components, the patent enables parallel production streams and simplified assembly processes, thereby maintaining high measurement accuracy without significantly extending production time.
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 sensor assembly effectively mitigates EMI noise, improves signal quality, and reduces manufacturing costs, providing a flexible and lightweight solution for non-invasive monitoring of tissue oxygenation levels with enhanced accuracy and ease of use.
Implementation Method 1
The light source is operative to emit light signals of a plurality of different wavelengths, including those in the near-infrared range. The light detector is operative to detect light emitted by the light source and passed through the subject's body tissue.
Implementation Method 2
The shielding, which is disposed around at least a portion of the light detector, attenuates local EMI and thereby reduces undesirable noise within the light detector signals.
Implementation Method 3
Hemoglobin exposed to light in the near-infrared range has specific absorption spectra that varies depending on its oxidation state; i.e., oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) each act as a distinct chromophore.
Data Source
AI summary
A spectrophotometric sensor assembly for non-invasive monitoring of a blood metabolite within a subject's body tissue is provided that includes a pad, a light source, and a light detector The light source is operative to emit light signals of a plurality of different wavelengths. The light detector is operative to detect light emitted by the light source and passed through the subject's body tissue. The light detector is at least partially enclosed in EMI shielding. In some embodiments, the light detector and EMI shielding are disposed in a detector housing that encloses the light detector and shielding. The housing is aligned with a detector aperture disposed in the pad.