Optical Sensing Unit for Wearable Device State Detection
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Solution Overview
Problem
Optical sensing units in wearable devices often fail to distinguish between return light from a user's body and an object, leading to inaccurate measurements and potential erroneous triggering of processes or components.
Innovation Solution
An electronic device with a plurality of light detectors and emitters is configured to differentiate between a user's body and an object by emitting light towards the strap and the device's edge, using optical components like Fresnel lenses to determine states such as being on-wrist or off-wrist, and sub-states like orientation relative to the body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical sensing unit is used to measure PPG signals, then the device structure remains simple, but the system cannot distinguish between return light from user's body and return light from an object, resulting in inaccurate measurements
Solution Approach 1:
The optical sensing unit is segmented into multiple independent light emitters (first light emitters for PPG measurement and second light emitters for state detection) and multiple light detectors. This segmentation allows the system to separately measure physiological signals and detect device state without interference, resolving the contradiction between measurement precision and device complexity by organizing functions into distinct modular components.
Solution Approach 2:
A processor acts as an intermediary that receives signals from both the light detectors and external sensors (accelerometer, gyro sensor), then integrates this information to determine device state. This intermediary processing layer enables the system to distinguish between user body reflections and object reflections by cross-referencing multiple data sources, improving measurement accuracy without requiring a completely complex optical structure.
2Use of energy by moving object
If the device continuously monitors PPG signals, then physiological data can be collected, but power consumption increases when the device is not properly positioned on the user's body
Solution Approach 1:
The system performs preliminary state detection using second light emitters and light detectors to determine whether the device is properly positioned on the user's body before initiating or continuing PPG signal measurement. This preliminary action prevents wasteful power consumption by avoiding continuous PPG monitoring when the device is off the body, while ensuring measurement validity is maintained when the device is properly positioned.
Solution Approach 2:
The system uses feedback from state detection (via second light emitters and external sensors) to dynamically control the operation of first light emitters and PPG processing. When the device detects it is not on the user's body, it feedbacks to stop or pause PPG measurement, reducing power consumption. When properly positioned, the feedback enables continuous monitoring to maintain measurement validity.
3Ease of operation
If the device operates in all environments without state detection, then the device complexity remains low, but inaccurate PPG measurements may erroneously trigger other processes or components
Solution Approach 1:
The system performs preliminary state verification using second light emitters and integrated sensors before automatically triggering PPG-based processes. This preliminary action ensures that automatic processes are only triggered when the device is properly positioned on the user's body and PPG measurements are valid, preventing erroneous triggering while maintaining ease of automatic operation.
Solution Approach 2:
The system continuously monitors device state through second light emitters and external sensors, providing feedback to control the automatic triggering of processes. When state detection indicates improper positioning or invalid PPG signals, the feedback mechanism prevents erroneous process triggering. When proper conditions are met, the feedback enables automatic processes to proceed, maintaining ease of operation.
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 configuration enhances measurement accuracy by correctly identifying the device's state, allowing for conditional operations like ignoring PPG signals or powering off components to reduce power consumption and improve security.
Implementation Method 1
The light received by the light detector can be light that has returned (e.g., reflected off) and exited the tissue
Implementation Method 2
Optical sensing units can be used to measure photoplethysmogram (PPG) signals
Implementation Method 3
one or more optical components, which can allow the plurality of second light emitters to emit first light towards the strap attached to the device and second light towards the edge of the device
Data Source
AI summary
Disclosed herein is an electronic device including an optical sensing unit for distinguishing between a user's body and an object. The optical sensing unit can include a plurality of light detectors, a plurality of first light emitters, and a plurality of second light emitters. The plurality of first light emitters can measure physiological information of the user, and the plurality of second light emitters can measure a state of the device. The device can include one or more optical components, which can allow the plurality of second light emitters to emit first light towards the strap attached to the device and second light towards the edges of the device.