PPG Sensor Optical Scatterer for Accurate Oxygen Saturation
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Solution Overview
Problem
Existing PPG sensors face challenges in accurately measuring oxygen saturation due to non-functional optical radiation, which can introduce calibration artifacts and reduce the signal-to-noise ratio, especially when non-pulsatile tissue is part of the optical path.
Innovation Solution
Incorporating an optical scatterer with a volume scattering material in the PPG sensor system to scatter non-functional optical radiation, redirecting it into functional optical radiation that contributes to the measurement, either before or after it interacts with bodily tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If non-functional optical radiation is allowed to reach the optical detector, then the detected signal intensity increases, but calibration artifacts are introduced and measurement accuracy deteriorates
Solution Approach 1:
The patent converts non-functional optical radiation (harmful) into functional optical radiation (beneficial) by using an optical scatterer to redirect it into the detector's field of view at angles that contribute to valid PPG measurements. This transforms the harmful shunt light into a useful signal source.
Solution Approach 2:
An optical scatterer is introduced as an intermediary component between the optical source and the detector. This scatterer mediates the interaction by redirecting non-functional optical radiation into functional paths, enabling the detector to receive additional signal without direct exposure to harmful shunt light.
2Length of stationary object
If optical radiation travels through non-pulsatile tissue (fat, bone, ligaments, nails), then the optical path length increases, but the modulation depth decreases and signal-to-noise ratio deteriorates
Solution Approach 1:
The optical scatterer creates local variation in optical path directions, redirecting radiation to preferentially sample pulsatile tissue regions while minimizing traversal through non-pulsatile structures. This local redirection improves the quality of detected signal by enhancing modulation depth.
3Measurement precision
If a black cushion material is used to absorb non-functional optical radiation, then calibration artifacts are reduced, but functional optical radiation that is backscattered is also absorbed and signal intensity decreases
Solution Approach 1:
The optical scatterer acts as an intermediary that redirects backscattered functional optical radiation away from the black cushion material, preventing its absorption. This allows the black cushion to maintain its function of blocking shunt light while the scatterer protects useful backscattered signal from being lost.
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
Increases the proportion of functional optical radiation, enhancing the signal-to-noise ratio and power efficiency, leading to more accurate and reliable oxygen saturation measurements.
Implementation Method 1
an optical scatterer coupled to the support structure and comprising a volume scattering material; wherein, in use, the optical scatterer is configured to scatter at least a portion of the emitted optical radiation
Data Source
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AI summary
Proposed concepts thus aim to provide schemes, solutions, concept, designs, methods and systems pertaining to measuring oxygen saturation of blood within bodily tissue. In particular, embodiments aim to provide a system for measuring oxygen saturation of blood within bodily tissue. This can be achieved by scattering some of the emitted optical radiation, such that at least some of the non-functional emitted optical radiation (e.g., that would not be directed towards tissue and/or into a optical radiation-absorbing cushion, for example) will be scattered in such a way that it will become functional optical radiation that contributes to the blood oxygen saturation measurement.