Flexible Substrate Emitter-Detector Array for Biometric Sensing
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Solution Overview
Problem
Wrist-worn devices for measuring heart rate via photoplethysmography (PPG) face accuracy issues due to rotation, which reduces the effectiveness of the limited light sources and detectors, leading to sparse arterial illumination and suboptimal measurement locations.
Innovation Solution
A monolithic integrated emitter-detector array on a flexible substrate, where emitters and detectors are embedded in a wearable device, allowing for selective activation and optimization based on signal quality, ensuring accurate biometric sensing even with device movement on the wrist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only one or two light sources and detectors are used in wrist-worn devices, then the device complexity is reduced and battery life is extended, but the measurement precision deteriorates due to sparse arterial illumination and suboptimal measurement locations caused by device rotation
Solution Approach 1:
The patent divides the single light source and detector into multiple segmented emitters and detectors arranged in arrays. This segmentation allows the system to illuminate multiple locations on the wrist simultaneously, increasing the probability of capturing arterial blood flow signals even when the device rotates, thereby improving measurement precision without requiring a single complex high-power component
Solution Approach 2:
The patent transitions from a single-point measurement approach to a multi-point spatial array configuration. By distributing emitters and detectors across multiple positions on the wrist, the system adds spatial dimensionality to the measurement, enabling it to maintain accuracy despite rotational movements that would affect a single fixed measurement point
2Adaptability or versatility
If multiple emitters and detectors are used in arrays, then the measurement precision and adaptability to device rotation are improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent implements dynamic control of the emitter and detector arrays through scanning circuits that selectively activate individual elements. Rather than continuously powering all array elements, the system dynamically selects and activates only the necessary subset of emitters and detectors based on current measurement requirements, thereby maintaining adaptability to rotation while reducing overall power consumption
Solution Approach 2:
The patent employs periodic scanning and selective activation of emitter-detector pairs rather than continuous operation of all elements. The scanning circuits periodically cycle through different combinations of array elements, enabling the system to maintain measurement capability across various rotational positions while consuming power only during active measurement intervals, thus reducing average power consumption
3Reliability
If continuous operation of all emitters and detectors is used, then complete coverage of the wrist area is achieved, but the power consumption increases and battery life decreases
Solution Approach 1:
The patent extracts and activates only the necessary subset of emitters and detectors from the complete array at any given time. Rather than operating all array elements continuously, the scanning circuits selectively extract and engage only those elements needed for current measurement conditions, thereby maintaining signal quality through adequate coverage while minimizing energy consumption by leaving other elements inactive
Solution Approach 2:
The patent implements a scanning approach where different subsets of emitter-detector pairs are activated in sequence rather than simultaneously. Elements that are not currently needed for measurement are effectively discarded (deactivated) to save power, while the system recovers measurement capability by activating different elements in subsequent scanning cycles, thus maintaining reliability over time while reducing instantaneous and average power consumption
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 solution enhances the accuracy and reliability of biometric measurements by optimizing emitter and detector usage, improving signal quality, and extending battery life through reduced power consumption.
Implementation Method 1
a first array of emitters embedded in the flexible substrate, the first array of emitters configured to emit first electromagnetic (EM) signals
Implementation Method 2
a first array of detectors embedded in the flexible substrate, the first array of detectors configured to detect reflections of the first EM signals
Data Source
AI summary
Examples of monolithic integrated emitter-detector array in a flexible substrate for biometric sensing and associated devices and methods are disclosed. One disclosed example device includes a flexible substrate; a first array of emitters embedded in the flexible substrate, the first array of emitters configured to emit first electromagnetic (EM) signals; a first array of detectors embedded in the flexible substrate, the first array of detectors configured to detect reflections of the first EM signals; a first scanning circuit coupled to the first array of emitters, the first scanning circuit configured to selectively activate individual emitters of the first array of emitters; and a first sensing circuit coupled to individual detectors of the first array of detectors, the first sensing circuit configured to receive a detection signal from at least one of the detectors of the first array of detectors.