Dual-Wavelength Optical Skin Sensor for Wearable Contact Detection
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Solution Overview
Problem
Conventional wearable devices struggle to accurately detect skin contact due to false positives from non-skin objects, leading to battery drain and operational noise, especially under unstable wearing conditions, and are limited in smaller devices like hearables.
Innovation Solution
An optical-based skin detection sensor using red and infrared light emitting units to determine skin contact by analyzing the ratio and change in intensity of reflected light, employing blind separation techniques to filter noise from movement, and a controller to differentiate skin based on normalized reflectance ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional skin detection methods (current flow, impedance, pressure) are used, then skin contact can be detected, but false positives occur when non-skin objects are detected, causing battery discharge and operational noise
Solution Approach 1:
The patent replaces conventional mechanical/electrical detection methods (current flow, impedance, pressure sensors) with an optical detection system that uses light emission and reflection characteristics to identify skin. The optical sensor detects skin by measuring reflected light intensity and spectral characteristics, which are unique to skin tissue, thereby eliminating false positives from non-skin objects and reducing unnecessary battery consumption.
Solution Approach 2:
The patent utilizes the optical properties and light reflection characteristics of skin tissue. By emitting light at specific wavelengths and measuring the reflected light's intensity and spectral signature, the system identifies skin based on its unique optical characteristics. This allows accurate differentiation between skin and non-skin objects, preventing false activations and associated battery drain.
2Reliability
If conventional skin detection methods are used, then skin contact can be detected, but large amounts of noise are generated under unstable wearing situations with movement, causing normal detection operation to fail
Solution Approach 1:
The patent replaces mechanical pressure sensors and electrical methods with optical detection that is inherently insensitive to mechanical movement. The optical sensor measures light reflection characteristics that remain stable despite device movement, allowing continuous reliable detection during unstable wearing situations without generating false noise or failing operational detection.
Solution Approach 2:
The patent employs dynamic signal processing techniques including moving average filtering and variance-based thresholding to distinguish between stable skin contact signals and transient noise caused by movement. The system adapts its detection thresholds based on signal variability, maintaining reliable operation during dynamic wearing conditions.
3Measurement precision
If highly sophisticated sensors are added to hearable devices for skin detection, then detection accuracy improves, but device size and complexity increase, which is not feasible for small hearable devices
Solution Approach 1:
The patent employs a simple, low-cost optical sensor module that can be easily integrated into small hearable devices. Rather than using complex sophisticated sensors, the system uses basic light emission and detection components with software-based signal processing to achieve accurate skin detection, making it feasible for compact device implementations.
Solution Approach 2:
The patent designs an optical sensor system that serves multiple functions: skin contact detection, wearability assessment, and signal quality validation. This multi-functional approach eliminates the need for separate sophisticated sensors, reducing overall device complexity while maintaining detection accuracy.
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 sensor accurately identifies skin contact even under unstable conditions, reducing battery waste and enabling convenient use of wearable devices by providing services like exercise coaching and sleep analysis.
Implementation Method 1
a first light emitting unit that outputs first output light of a first wavelength range; a second light emitting unit that outputs second output light of a second wavelength range
Implementation Method 2
a light receiving unit that senses first reflected light and second reflected light reflected, respectively, from a predetermined object
Implementation Method 3
an optical-based skin detection sensor that determines whether a detected object is skin based on reflected light output and reflected from a plurality of light emitting units
Data Source
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AI summary
The optical-based skin detection sensor according to an example of the present invention, comprises a first light emitting unit that outputs first output light of a first wavelength range; a second light emitting unit that outputs second output light of a second wavelength range different from the first wavelength range; a light receiving unit that senses first reflected light and second reflected light reflected, respectively, from a predetermined object in which the first output light and the second output light are detected within a predetermined distance; and a controller that determines whether the predetermined object is skin based on reflected light data for the first reflected light and the second reflected light sensed in the light receiving unit.