PPG Sleep Monitoring Control to Prevent Bedtime Light Leakage
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Solution Overview
Problem
Wearable devices equipped with photoplethysmography (PPG) sensors often disrupt sleep quality due to light emission, especially when users are in bed but not asleep, as they continuously emit visible light to monitor vital signs.
Innovation Solution
A vital-sign detection system that automatically disables the PPG sensor when the user gets into bed but has not fallen asleep, using a controller to switch between enabled and disabled modes based on predetermined events, such as bed entry and sleep onset, thereby stopping light emission until the user falls asleep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PPG sensor continuously emits visible light to monitor vital signs, then the monitoring function is maintained, but the sleep quality of the user is disrupted due to light leakage
Solution Approach 1:
The patent applies the dynamics principle by making the PPG sensor's operational state changeable based on detected events. The sensor transitions between enabled and disabled modes dynamically according to the user's state (awake vs. asleep), rather than operating in a fixed continuous mode. This resolves the contradiction by adapting the monitoring function to different temporal contexts.
Solution Approach 2:
The patent implements periodic action through event-driven sampling of sensor data at specific intervals (e.g., every 30 seconds) and periodic mode switching based on detected events. The system periodically evaluates whether to enable or disable the PPG sensor based on motion and light sensor readings, creating a rhythm of monitoring that respects sleep cycles while maintaining health tracking.
2Object-affected harmful factors
If the PPG sensor is disabled to prevent light leakage, then sleep quality is improved, but the continuous monitoring of vital signs is interrupted
Solution Approach 1:
The patent applies preliminary action by detecting events (such as motion cessation and darkness) before the user actually falls asleep, and disabling the PPG sensor in advance. The system proactively switches to disabled mode based on predictive indicators of sleep onset, ensuring light leakage prevention begins before the user is fully asleep while maintaining monitoring readiness.
Solution Approach 2:
The patent implements feedback through continuous monitoring of motion and light sensor data to determine when to switch the PPG sensor between modes. The system uses feedback loops where sensor readings are evaluated against thresholds, triggering mode transitions that are then monitored for effectiveness, creating a closed-loop control system that balances sleep quality with monitoring continuity.
3Reliability
If the PPG sensor operates in enabled mode during bed entry, then vital signs are monitored, but light leakage occurs when the user is in bed but not asleep
Solution Approach 1:
The patent applies segmentation by dividing the nighttime period into distinct operational phases: an initial monitoring phase when the user enters bed, and a subsequent sleep phase when monitoring is suspended. The system segments the operational timeline based on detected events (motion, light levels), allowing different PPG sensor states for different phases of the night.
Solution Approach 2:
The patent implements parameter changes by switching the PPG sensor's operational parameter (enabled/disabled state) based on detected environmental and physiological parameters. The system monitors motion amplitude, light intensity, and time duration, then changes the PPG sensor's operational parameter accordingly, transitioning from enabled during bed entry to disabled during confirmed sleep periods.
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 effectively prevents light leakage from affecting sleep quality by only enabling the PPG sensor when the user is asleep, enhancing sleep experience while still allowing for continuous monitoring of vital signs.
Implementation Method 1
a PPG sensor which operates to obtain PPG information comprises a light emitter emitting visible light (green light)
Data Source
AI summary
A vital-sign detection system is provided. The vital-sign detection system includes a vital-sign detection device and a controller. The vital-sign detection device is enabled to detect a vital-sign of a user. The controller determines whether the gets in the bed and controls the vital-sign detection device to switch to a disabled mode from a first enabled mode in response to the user getting in the bed. During a period when the vital-sign detection device is in the disabled mode, the controller determines whether the user falls asleep. In response to the user falling asleep, the controller controls the vital-sign detection device to switch to a second enabled mode from the disabled mode.