Wrist-Worn Optical Cardiac Monitor With Parallel Signal Paths
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Solution Overview
Problem
Conventional optical cardiac monitors often experience reduced signal quality due to the presence of wrist structures, such as bones and ligaments, which interfere with optical signals, leading to inaccurate heart rate and pulse oximetry measurements when the device is tilted or moved during user activity.
Innovation Solution
The wrist-worn electronic device employs multiple optical transmitters and receivers arranged in parallel paths along the arm axis to minimize interference from wrist structures, ensuring higher signal-to-noise ratios by avoiding signal paths that cross or are proximate to these structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single optical transmitter and receiver are used in conventional cardiac monitors, then the device structure is simple, but the signal-to-noise ratio decreases when the device is tilted or moved during user activity due to interference from wrist structures
Solution Approach 1:
The optical monitoring system is segmented into multiple independent optical transmitters and receivers arranged in parallel paths. Each optical path operates independently to provide multiple signal sources, allowing the system to select or combine signals based on quality metrics. This segmentation enables the system to maintain reliable cardiac monitoring even when some paths are affected by wrist structure interference.
Solution Approach 2:
The system changes the spatial parameter of optical signal paths by arranging transmitters and receivers at different positions and orientations on the wristband. Multiple signal paths with different geometries are created, and the system dynamically selects or weights paths based on their signal quality parameters, thereby adapting to varying wrist positions and movement conditions.
2Measurement precision
If optical signal paths cross or are proximate to wrist structures (bones and ligaments), then the device can be compact, but measurement precision deteriorates due to signal interference
Solution Approach 1:
Different optical paths are designed with different local qualities - some paths are intentionally routed to avoid wrist structures while others may pass closer to them. The system evaluates the local signal quality of each path and selectively uses paths with superior local quality (lower interference) for cardiac parameter measurement, thereby achieving high measurement precision without requiring all paths to be complexly routed.
Solution Approach 2:
The system adds spatial dimensionality to the optical measurement by creating multiple signal paths that diverge in different directions relative to the wrist structures. Instead of a single linear path, the optical signals propagate through multiple spatial dimensions, allowing the system to find paths that circumvent bones and ligaments, thus improving measurement precision while managing device complexity.
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
This configuration allows for accurate and reliable determination of physiological information, such as heart rate and pulse oximetry, by selecting PPG signals with minimal noise, even during user movement or tilting.
Implementation Method 1
an optical receiver, which receives transmissions or reflections of the optical signal from the skin and generates a photoplethysmogram (PPG) signal corresponding to the intensity of the received optical signal
Data Source
AI summary
A wrist-worn electronic device comprises a housing including a bottom wall configured to contact a user's wrist, three optical transmitters, an optical receiver and a processor. The first optical transmitter, the second optical transmitter and the third optical transmitter transmit a plurality of optical signals, each having a unique wavelength, that pass through a user's skin and are received by the optical receiver that generates corresponding electronic signals. The optical signals output by the first optical transmitter traveling along a first signal path, the optical signals output by the second optical transmitter traveling along a second signal path and the optical signals output by the third optical transmitter traveling along a third signal path, wherein the first signal path substantially overlaps with the second signal path and the third signal path. The processor is configured determine physiological information about the user based on the electronic signals.