Device, system and method for detection and processing of heartbeat signals
Inventors
TOGNETTI, SIMONE • CENCI, IVAN • RESNATI, DANIELE • GARBARINO, MAURIZIO • LAI, MATTEO
Assignees
Publication Number
US-12262979-B2
Publication Date
2025-04-01
Expiration Date
2034-01-21
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Abstract
A heart beat detection device comprises at least one optical reflection sensor to be positioned on the skin of a person. The sensor unit is provided with a light emitter and a corresponding light receiver which converts the light reflected by the skin into an electric signal and comprises electrically adjustable optical filters connected to the emitter, to the receiver or to both of them in order to select, upon operation, a desired light wavelength and perform processing of the signals thus obtained in order to reinforce the heart beat signal. A system with this device and a detection method are also described.
Core Innovation
The invention relates to a heart beat detection device comprising at least one optical reflection sensor unit positioned on the skin of a person. The device includes a light emitter and a light receiver converting reflected light into an electric signal and is equipped with electrically adjustable optical filters connected to the emitter, receiver, or both. These filters enable dynamic selection of desired wavelengths of light to reinforce the heart beat signal by differentiating between multiple optical effects such as absorption and fluorescence.
The problem addressed is that known optical heart beat detection systems, especially reflection devices used on convenient body zones like the wrist, suffer from a small variation in reflected light related to blood flow and are significantly affected by noise. This noise arises from mechanical deformation of skin and tissues, external light conditions, and relative movement between the sensor and underlying tissue, notably during physical activity. Prior art solutions involving movement sensors, dual wavelength sources, or combinations thereof do not adequately improve the signal-to-noise ratio under all conditions, particularly when the wearer is free to perform daily activities.
The invention provides a heart beat detection device with tunable optical filters to select wavelengths dynamically in absorption and fluorescence modes. By combining signals at these wavelengths, the system improves signal to noise ratio and adapts to individual skin characteristics such as complexion, tanning, and tissue composition. Additionally, the device may use a pair of sensors spaced along the blood flow direction to estimate transit time of blood and thereby identify noise due to tissue movement. The device can further incorporate electrical conductivity measurement of the skin and a mechanical detection system for acceleration to refine signal processing and noise reduction. The use of adjustable filters, combined signals, and movement or conductivity measurements enables a more reliable heart beat detection across various conditions and user movements.
Claims Coverage
The patent includes multiple independent claims covering devices and systems for heart beat detection with optical sensors, conductivity measurement, adjustable optical filters, and signal processing units.
Inclusion of conductivity sensor with polarity inversion
A strap configured to be fastened to a wrist comprising a conductivity sensor to measure skin conductivity, where the sensor periodically inverts polarity to reduce polarization and electrolysis effects.
Combination of conductivity and optical signals to improve signal/noise ratio
A signal processing unit that combines the measured conductivity and optical electric signal to improve the signal/noise ratio for determining heart beat.
Use of two optical sensor units spaced to estimate blood propagation time and adjust detection
Two optical sensor units arranged at a distance for estimating blood propagation time, with processing to modify detected signals based on variation in this propagation time to reduce noise from tissue movement.
Incorporation of accelerometer with adaptive filtering
An accelerometer measuring acceleration of the device, with a signal processing unit that modifies the electric signal based on the acceleration by subtracting acceleration via an adaptive numerical filter.
Variable luminosity control to optimize signal above threshold
A power supply element controlled to vary light emitter luminosity ensuring the electric signal remains above a predefined minimum threshold, optimizing signal quality and power consumption.
Use of a sealing ring to reduce ambient light and moisture
A sealing ring coupled to the optical sensor units to reduce entry of ambient light and moisture to improve measurement accuracy and sensor reliability.
The claims collectively cover a heart beat detection device incorporating an optical sensor system with dynamically adjustable filters, a conductivity sensor with polarity inversion, paired sensors to estimate blood propagation time, an accelerometer for motion compensation, a control of emitted light intensity, and protective features such as sealing rings. These inventive features contribute to enhanced signal quality and robustness under various usage conditions.
Stated Advantages
Improved detection of heart beat signals with a higher signal/noise ratio by using electrically adjustable optical filters selectable for absorption and fluorescence wavelengths.
Ability to adapt measurement wavelengths dynamically to individual skin characteristics such as complexion, tanning, and physiological changes over time.
Noise reduction by compensating for tissue movement and mechanical deformation via paired optical sensors estimating blood transit time and accelerometer data for motion artifacts.
Use of conductivity measurement of skin combined with optical signals to further improve heart beat signal quality and reduce noise.
Optimized battery life by dynamically adjusting the luminous intensity of the light emitter to maintain signal strength above a minimum useful threshold only as needed.
Documented Applications
Wearable heart rate monitoring devices positioned on the wrist, such as wrist-watches or bracelets, for continuous monitoring during daily activities including physical exercise.
Remote physiological data detection and processing systems communicating wirelessly with external terminals or servers for health monitoring and analysis.
Application in indicating physiological parameters related to stress state, physical activity level, physical condition, sleep quality, or excitation based on detected heart beat signals.
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