Optical Mouse Lift Detection Using Dual Thresholds
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Solution Overview
Problem
Existing optical pointing devices face challenges in reliably detecting the lift condition, leading to inefficient power consumption and false detection issues due to the reliance on a fixed loss-of-focus threshold, which is not suitable for various surfaces, causing spurious motion detection and interrupting normal operation.
Innovation Solution
Implementing a dual threshold system where a lower threshold is used when the device is moving and a higher threshold when it is at rest, with the flash rate adjusted based on motion speed, and dynamically adjusting the loss-of-focus threshold based on the average number of motion features detected, allowing for reliable lift condition detection and power savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed loss-of-focus threshold is used for lift detection, then the device can detect lift condition, but it causes false detection on various surfaces and spurious motion detection
Solution Approach 1:
The patent implements a dual threshold system where the loss-of-focus threshold dynamically changes based on device state: a lower threshold is used when the device is moving to maintain sensitivity, while a higher threshold is used when the device is at rest to prevent false detections. This dynamic adjustment resolves the contradiction by adapting the threshold to operational context rather than using a fixed value.
Solution Approach 2:
The patent changes the threshold parameter based on the device's motion state and surface characteristics. By monitoring motion features and adjusting the loss-of-focus threshold accordingly, the system adapts to different surfaces and operational conditions, preventing false lift detections while maintaining accurate detection capability.
2Measurement precision
If the optical pointing device is lifted, then the sensor goes out of focus and sees less motion features, but noise becomes dominant and spurious motion is detected
Solution Approach 1:
The patent uses feedback from the motion sensing unit to continuously monitor the number of motion features detected. When the count falls below the dynamically adjusted loss-of-focus threshold, the system identifies this as a lift condition. This feedback mechanism allows the system to distinguish between legitimate motion and spurious noise by comparing actual motion feature counts against expected thresholds.
Solution Approach 2:
The system dynamically adjusts the loss-of-focus threshold based on whether the device is in motion or at rest. When the device is moving, a lower threshold allows detection of legitimate motion features. When at rest, a higher threshold filters out noise and prevents false lift detection, thus adapting the system's sensitivity to current operational conditions.
3Reliability
If a high loss-of-focus threshold is used, then lift condition is detected reliably, but false lift detection occurs on surfaces with small motion features
Solution Approach 1:
The patent implements dynamic threshold adjustment based on device state. When the device is moving, a lower threshold is applied to accommodate surfaces with fewer motion features, preventing false lift detections. When the device is at rest, a higher threshold is applied to ensure reliable lift detection. This state-dependent thresholding resolves the contradiction between reliability and false detection.
4Use of energy by moving object
If the device enters sleep mode to save power, then power consumption is reduced, but false lift detection prevents entering sleep mode
Solution Approach 1:
The patent uses dynamic threshold adjustment based on motion state to enable accurate lift detection. When the device is at rest and no lift is detected (motion features above threshold), the system can confidently enter sleep mode to save power. When motion is detected or the device is already in motion, the lower threshold ensures lift conditions are properly detected, preventing premature sleep mode entry. This resolves the contradiction by making sleep mode entry decisions based on reliable, context-aware lift detection.
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 approach ensures accurate detection of the lift condition, enabling the device to enter sleep mode and conserve power while minimizing false detections, thus improving user convenience and power efficiency across different surfaces.
Implementation Method 1
detecting a light intensity pattern of illuminated portion surface S by means of light source 110
Implementation Method 2
photodetector array 120 including a plurality of pixels aligned along first and second axes for detecting a light intensity pattern
Data Source
AI summary
A method for detecting a lift condition from an illuminated surface portion of an optical motion sensing device. According to a first embodiment, two different “loss-of-focus” thresholds are used. A first threshold is used when the optical pointing device is not moving, and a second threshold greater than the first one is used when the optical pointing device is moving. The optical device further requires means for detecting whether it is moving or not. According to a second embodiment, a dynamical loss-of-focus threshold depending on an average number of motion features that the surface exhibits to the sensor of the optical pointing device is used.