Vital Sign Sensor Light-Scattering Layer Reduces Motion Artifacts
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Solution Overview
Problem
Vital sign sensors face inaccuracies due to motion artifacts caused by changes in position relative to the skin, leading to unreliable heart rate measurements.
Innovation Solution
A vital sign sensor design featuring a transparent first layer and a light-scattering second layer, where the emitter is embedded in the first layer and the detector is embedded in a non-light-scattering potting compound, with the light-scattering layer increasing the effective emissive area to reduce motion artifacts and enhance signal reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the emitter is placed directly on the skin, then the light coupling is strong, but motion artifacts cause signal inaccuracies
Solution Approach 1:
The sensor is segmented into multiple independent light-emitting elements (red LED, green LED, infrared LED) arranged in an array, each capable of emitting light independently. This segmentation allows the sensor to maintain stable measurements during motion by distributing the measurement function across multiple elements rather than relying on a single point of contact
Solution Approach 2:
The light-emitting elements are arranged in a two-dimensional array pattern on the sensor surface, transitioning from a single-point contact to a distributed area contact. This dimensional change increases the effective measurement area, making the sensor less sensitive to position changes and motion artifacts while maintaining strong light coupling with the skin
2Reliability
If the sensor area is increased to reduce motion artifacts, then the effective emissive area increases, but the device size and power consumption increase
Solution Approach 1:
The sensor dynamically activates only the specific light-emitting elements needed for the current measurement, rather than illuminating the entire array continuously. This dynamic operation allows the sensor to maintain signal reproducibility while reducing power consumption by selectively engaging individual LEDs based on measurement requirements
Solution Approach 2:
Different regions of the sensor array have different functional properties, with specific red, green, and infrared LEDs positioned to target different tissue depths and vascular beds. This local quality differentiation allows efficient light emission from only the necessary elements, reducing overall power consumption while maintaining measurement reliability
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
The design reduces the impact of motion artifacts, providing more reliable and reproducible heart rate measurements while maintaining efficiency for battery-powered applications like wearables.
Implementation Method 1
The light 5 emitted by the emitter 2, for example a light emitting diode (LED), propagates in the skin 4 and is partly absorbed by the blood in the blood vessels.
Implementation Method 2
a second layer of a light scattering material arranged on the first layer. The emitter component is embedded in the first layer.
Data Source
AI summary
In an embodiment a vital sign sensor includes an emitter component configured to emit light, a detector component configured to detect light, a first layer of a substantially transparent material, wherein the emitter component is embedded in the first layer, and a second layer of a light scattering material arranged on the first layer, wherein the second layer includes converter particles, and wherein the first layer and the second layer are surrounded by at least one wall of a reflective material.