Optical Sensor Device Removal Detection Using Adaptive Thresholds
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Solution Overview
Problem
Existing wearable devices struggle to accurately detect when they have been removed from a user, particularly due to variations in user body characteristics, device wear types, and band types, leading to potential security risks and power consumption issues.
Innovation Solution
The implementation of an optical sensor system with electromagnetic radiation emitters and detectors, which measures the amount of radiation reflected or scattered from the user's body and compares it to various thresholds to determine device removal, including loose wear, time-lapsed, and instant-off thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single object proximity threshold is used to detect device removal, then the detection process is simple, but it cannot accurately account for variations in user body characteristics, device wear types, and band types
Solution Approach 1:
The patent applies parameter changes by implementing multiple object proximity thresholds (first threshold, second threshold, third threshold) with different sensitivity levels. The first threshold is less sensitive and generates a first indication, the second threshold is more sensitive and generates a second indication, and the third threshold provides additional detection granularity. This multi-threshold approach allows the system to adapt to variations in user body characteristics, device wear types, and band types while maintaining accurate device removal detection.
2Measurement precision
If multiple object proximity thresholds are used to improve detection accuracy, then detection precision improves, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the detection process into distinct stages using different thresholds. The first threshold provides a preliminary indication, the second threshold provides a more sensitive indication, and the third threshold adds further detection granularity. Each threshold operates semi-independently, allowing the system to achieve high detection precision without requiring all thresholds to be simultaneously complex. The segmented approach simplifies the overall system design while maintaining accuracy.
3Speed
If device removal is detected quickly using instant-off threshold, then response time is reduced, but false detections may increase due to transient signals
Solution Approach 1:
The patent applies preliminary action by using the first object proximity threshold (less sensitive threshold) as a preliminary detection stage. When the first threshold generates a first device removal indication, this serves as a preliminary signal that triggers further evaluation using the second and third thresholds. This preliminary action allows the system to quickly respond to potential removal events while maintaining reliability through subsequent verification stages, reducing false detections from transient signals.
4Reliability
If a less sensitive threshold is used to reduce false detections, then detection reliability improves, but response time increases
Solution Approach 1:
The patent applies periodic action through the sequential evaluation of multiple thresholds. The system periodically checks object proximity using the first threshold, then the second threshold, and finally the third threshold in a structured sequence. This periodic multi-stage evaluation ensures reliable detection by verifying removal across multiple threshold levels while managing response time through efficient sequential processing rather than continuous monitoring at all threshold levels simultaneously.
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 enables accurate detection of device removal, reducing security risks and power consumption by using adaptive thresholds and multiple optical measurement paths to account for different user and device configurations.
Implementation Method 1
an amount of electromagnetic radiation emitted by an electromagnetic radiation emitter and returned to an electromagnetic radiation detector over one of the optical measurement paths (e.g., an amount of electromagnetic radiation that reflects or scatters off of an object, such as a user's wrist or other body part)
Implementation Method 2
an amount of electromagnetic radiation emitted by an electromagnetic radiation emitter and returned to an electromagnetic radiation detector over one of the optical measurement paths (e.g., an amount of electromagnetic radiation that reflects or scatters off of an object, such as a user's wrist or other body part)
Data Source
AI summary
An electronic device includes a device body having a back surface, a band configured to fasten the device body to a user with the back surface facing a body part of the user, an optical sensor system, and a device removal detector. The optical sensor system has a first optical measurement path and a second optical measurement path. The first optical measurement path has a first optical path length that differs from a second optical path length of the second optical measurement path. The device removal detector is configured to generate a device removal indication responsive to either of, a first set of object proximity measurements received from the optical sensor system for the first optical measurement path, or a second set of object proximity measurements received from the optical sensor system for the second optical measurement path.