Wrist-worn Pulse Rate Sensor with Multi-Wavelength Light Control
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Solution Overview
Problem
Existing physiological property determination apparatuses face challenges in accurately determining pulse rates due to variations in light sources and body tissues, leading to reduced accuracy.
Innovation Solution
A physiological property determination apparatus with at least two light sources emitting light beams of different wavelengths, a two-dimensional light detector, and a controller that optimizes light intensities to prevent overload and distinguish signal fluctuations caused by motion, using techniques like principal component analysis to improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources with different wavelengths are used to improve measurement accuracy, then the signal-to-noise ratio is optimized, but the light detector may become overloaded
Solution Approach 1:
The controller dynamically adjusts the intensity of each light source based on real-time detection feedback. The system monitors the total light signal received by the detector and modulates individual light source intensities to maintain optimal signal-to-noise ratio while preventing detector saturation, enabling adaptive optimization across varying physiological conditions
Solution Approach 2:
The system changes the intensity parameter of each light source independently based on wavelength-specific optimization requirements. By adjusting intensity parameters dynamically rather than using fixed values, the system optimizes the contribution of each wavelength to the overall measurement while maintaining detector operation within linear response range
2Measurement precision
If the light intensity is increased to improve signal quality, then the measurement accuracy improves, but motion-induced noise and artifacts increase
Solution Approach 1:
The system segments the total light signal into wavelength-specific components and processes each separately. By analyzing temporal variations in each wavelength channel independently and then combining results, the system can distinguish physiological pulse signals from motion artifacts that affect wavelengths differently, improving signal quality while maintaining robustness against motion noise
Solution Approach 2:
The system uses feedback from temporal signal analysis to distinguish between physiological variations and motion artifacts. By monitoring the characteristics of light intensity fluctuations over time and comparing them against expected physiological patterns, the controller can identify and compensate for motion-induced noise, maintaining measurement accuracy during movement
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 approach enhances the accuracy of pulse rate determination by optimizing illumination and signal processing, reducing the impact of motion-induced noise and ensuring reliable measurements.
Implementation Method 1
at least two light sources for emitting at least two light beams having different wavelengths into tissue of the person... a light detector having a two-dimensional detection surface for detecting light, which has travelled through the tissue, wavelength-dependently
Implementation Method 2
a controller for separately controlling the intensities of the light beams of the different light sources such that the light detector is not overloaded
Implementation Method 3
US 2010/0268094 A1 discloses an apparatus for determining a pulse rate of a person... the pulse rate is determined based on variations of the detected light
Data Source
AI summary
The invention relates to a physiological property determination apparatus (1) for determining a physiological property like a pulse rate of a person. The apparatus may be configured to be worn on the wrist like a watch. A controller (8) separately controls at least two light sources (3, 4, 5) for emitting at least two light beams having different wavelengths into tissue of the person and a light detector (6) having a two-dimensional detection surface (12) detects light, which has travelled through the tissue, wavelength-dependently and generates a wavelength-dependent two-dimensional image based on the detected light. Based on the generated wavelength-dependent two-dimensional image the physiological property is determined. The separate control of the light sources allows for an independent optimization of the illumination and detection processes for each wavelength, which in turn can lead to an improved determination of the physiological property based on the wavelength-dependent two-dimensional image.