Concentric Optical Sensing Layout for Low-Crosstalk PPG Detection
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Solution Overview
Problem
Optical sensing systems face challenges due to optical losses affecting the determination of physiological information, particularly in photoplethysmogram (PPG) signals, which can be exacerbated by components within the system.
Innovation Solution
A concentric architecture is employed with a plurality of light detectors arranged around light emitters, including first and second emitters emitting different wavelengths, and a selective transparent layer with varying transparency to these wavelengths, along with a Fresnel lens and optical isolation to enhance measurement accuracy and reduce optical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light detectors are placed close to light emitters to improve signal strength, then measurement sensitivity improves, but optical crosstalk and interference increase
Solution Approach 1:
The patent applies local quality by creating wavelength-specific optical paths using selective transparent layers. Different regions of the optical sensing unit have different transparency properties: the first selective transparent layer is transparent to first wavelengths (e.g., red light) while blocking second wavelengths (e.g., infrared), and the second selective transparent layer is transparent to second wavelengths while blocking first wavelengths. This allows detectors to receive signals from specific emitters without interference, resolving the contradiction between proximity for sensitivity and separation for crosstalk reduction.
2Adaptability or versatility
If multiple light emitters with different wavelengths are used to enhance measurement capabilities, then measurement versatility improves, but optical interference and signal contamination increase
Solution Approach 1:
The patent segments the optical sensing unit into distinct wavelength channels using multiple selective transparent layers. Each layer is configured to transmit specific wavelength ranges while blocking others, effectively dividing the optical path into separate channels. This segmentation allows multiple emitters with different wavelengths to operate simultaneously without interference, maintaining measurement versatility while eliminating optical interference.
Solution Approach 2:
The selective transparent layers act as intermediaries between light emitters and detectors. These layers mediate the optical interaction by selectively transmitting or blocking specific wavelengths, preventing direct interference between different wavelength channels while still allowing the desired light signals to pass through to the appropriate detectors.
3Device complexity
If a single channel is used for all light detectors to simplify processing, then device complexity reduces, but measurement precision and signal differentiation deteriorate
Solution Approach 1:
The patent implements dynamic channel association where the mapping between light detectors and processing channels can change based on operational requirements. The system can dynamically assign detectors to different channels depending on which light emitter is active and what measurement is being performed. This dynamic reconfiguration allows the system to maintain low complexity by using a single physical channel while achieving high measurement precision through software-based channel differentiation.
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 concentric architecture improves measurement sensitivity and accuracy by optimizing detector placement and wavelength-specific transparency, allowing for dynamic channel association and enhanced signal-to-noise ratio (SNR) in PPG signal detection.
Implementation Method 1
In some examples, a Fresnel lens can be located in a corresponding region of the first and second light emitters. The Fresnel lens can include a plurality of regions, such as a first region and a second region. The first region can be located in the field of view(s) of the first light emitter(s), and the second region can be located in the field of view(s) of the second light emitter(s).
Implementation Method 2
Examples of the disclosure further include a selective transparent layer overlaying the plurality of light detectors. The selective transparent layer can include a plurality of first sections transparent to a second wavelength range (e.g., infrared wavelengths) and non-transparent to a first wavelength ranges (e.g., visible wavelengths).
Data Source
Figure 1A~1C
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Figure 2B
AI summary
An electronic device including optical sensing with a concentric architecture and methods for operation thereof is disclosed. The concentric architecture can include light detector(s) arranged in a concentric manner around light emitter(s). In some examples, at least one light emitter can be located in the center of the device, and each light detector can be located the same separation distance from the light emitter. Each light detector can be arranged such that the separation distance from the centrally located light emitter can be greater than the separation distance from another light emitter. Examples of the disclosure further include a selective transparent layer overlaying the light detector(s). The selective transparent layer can include section(s) transparent to a first wavelength range and non- transparent to a second wavelength ranges. In some examples, the selective transparent layer can further include section(s) transparent to the second wavelength range.