Optical Waveguide Layers for Wearable Biometric Sensors
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Solution Overview
Problem
Existing wearable biometric devices for optical biometric measurements, such as heart rate and blood oxygen level monitoring, are uncomfortable and have short battery life due to high power consumption and bulkiness, requiring tight skin contact to avoid movement artifacts.
Innovation Solution
A wearable apparatus with a flexible substrate, embedded light sources and photodetectors, and layers of optical material that guide light away from the photodetectors, using ambient light and a low power amplifier circuit, attached to the skin with a skin-safe adhesive, reducing direct light exposure and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the illumination is made very bright to attain a sufficient signal, then the measurement signal quality is improved, but the power consumption increases
Solution Approach 1:
The patent introduces optical waveguide layers as intermediary structures between the light source and photodetector. These waveguide layers channel and direct the light from the LED towards the photodetector, improving light utilization efficiency. This allows the system to achieve sufficient signal quality with lower illumination intensity, thereby reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The patent modifies the optical parameters of the system by implementing specific waveguide layer configurations with particular refractive indices and thicknesses. By optimizing these optical parameters, the system achieves more efficient light transport and detection, allowing for reduced LED brightness while maintaining adequate signal levels, thus lowering power consumption.
2Reliability
If the device is worn tightly on the skin to avoid movement artifacts, then the measurement reliability is improved, but the comfort and ease of operation deteriorates
Solution Approach 1:
The patent transitions from requiring tight mechanical contact (one-dimensional pressure contact) to achieving optical coupling through waveguide layers (multi-dimensional optical path management). The waveguide layers create dedicated optical pathways that maintain light transmission efficiency even when the device is worn more comfortably with less tight contact, thus preserving measurement reliability while improving comfort.
Solution Approach 2:
The optical waveguide layers act as intermediary structures that decouple the mechanical contact requirement from the optical coupling requirement. These layers ensure efficient light transport between the LED and photodetector regardless of slight variations in skin contact pressure, allowing the device to be worn comfortably without compromising measurement reliability.
3Ease of operation
If the device size is reduced to be suitable for skin attachment, then the ease of operation is improved, but the power source size is limited causing short usage time
Solution Approach 1:
The optical waveguide layers serve as intermediary structures that significantly improve light transport efficiency between the compact LED and photodetector. This enhanced optical coupling allows the system to use smaller, lower-capacity power sources while still achieving sufficient signal quality, thereby extending usable battery life despite the reduced power source size required for skin-attachable form factor.
Solution Approach 2:
The patent optimizes optical parameters such as waveguide layer refractive indices, thicknesses, and geometries to maximize light extraction and detection efficiency. These parameter optimizations enable the system to achieve adequate signal levels with lower power consumption, effectively extending usage time despite the size constraints on the power source.
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
Enables comfortable, long-term biometric measurements with reduced motion artifacts and improved battery life by minimizing direct light exposure to photodetectors and utilizing ambient light, thus enhancing the usability of wearable biometric devices.
Implementation Method 1
the first and second layer of optical material are configured to guide light from the at least one light source and to prevent the light from the at least one light source directly reaching the at least on photodetector
Implementation Method 2
the second layer of optical material is configured to guide light towards the at least one photodetector
Implementation Method 3
The apparatus may further comprise a reflective layer and an optical element configured to function as a waveguide
Data Source
AI summary
An apparatus comprising at least one light source, at least one photodetector, a first layer of optical material configured to embed the at least one light source, and a second layer of optical material configured to embed the at least one photodetector. The first and second layer of optical material are configured to guide light from the at least one light source and to prevent the light from the at least one light source directly reaching the at least on photodetector, and the second layer of optical material is configured to guide light towards the at least one photodetector.