Dynamic SQUAL Threshold for Optical Navigation Lift
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Solution Overview
Problem
Optical navigation devices often exhibit unwanted cursor movement when lifted from a surface due to pixel saturation and changes in light reflection, leading to unreliable motion tracking.
Innovation Solution
A method involving a SQUAL threshold management system that adjusts the saturation threshold based on pixel saturation levels and image characteristics to prevent unwanted cursor movement by suspending motion tracking information output when saturation exceeds a certain level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical navigation device uses a fixed SQUAL threshold for motion tracking, then the device structure remains simple, but unwanted cursor movement occurs when the device is lifted from the surface due to pixel saturation
Solution Approach 1:
The SQUAL threshold is transformed from a fixed value to a dynamic value that automatically adjusts based on real-time pixel saturation levels. The threshold management engine continuously monitors saturation and modifies the threshold accordingly, allowing the system to adapt to different operating conditions (surface contact vs. lift) without increasing structural complexity
Solution Approach 2:
A feedback loop is established where the threshold management engine monitors pixel saturation levels and uses this information to adjust the SQUAL threshold. This closed-loop control ensures that the threshold remains appropriate for current operating conditions, preventing unwanted cursor movement during lift while maintaining reliable tracking during surface contact
2Productivity
If the optical navigation device continues to output motion tracking information during lift, then the system operates continuously without interruption, but cursor movement becomes unreliable and unwanted
Solution Approach 1:
The system uses real-time feedback from pixel saturation monitoring to determine when to suspend motion tracking output. When saturation exceeds the dynamic threshold during lift, the system automatically suspends tracking information output, preventing unreliable cursor movement while maintaining operational readiness for when the device returns to the surface
3Reliability
If the SQUAL threshold is increased to prevent unwanted movement during lift, then cursor stability improves during lift conditions, but motion tracking sensitivity decreases during normal surface contact
Solution Approach 1:
The SQUAL threshold dynamically adapts its value based on operating conditions: it increases during lift (when pixel saturation occurs) to prevent unwanted cursor movement, and returns to normal levels during surface contact to maintain tracking sensitivity. This dynamic adjustment resolves the contradiction by applying different threshold levels at different times rather than using a single fixed threshold
Solution Approach 2:
The system changes the SQUAL threshold parameter in response to changes in pixel saturation levels. When saturation increases during lift, the threshold is increased to suppress false motion signals. When saturation returns to normal during surface contact, the threshold decreases to restore tracking sensitivity, thus maintaining both stability and precision across different operating conditions
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
Effectively reduces unwanted cursor movement by dynamically adjusting the SQUAL threshold in response to pixel saturation and image contrast, ensuring reliable motion tracking during lift conditions.
Implementation Method 1
the light source is mounted such that its light is ideally reflected from the surface to the image sensor
Implementation Method 2
an image sensor to acquire a series of digital images of the surface
Data Source
AI summary
A system and method for tracking movement between a surface and an optical navigation device are described. In an embodiment, the optical navigation device has an image sensor that includes an array of pixels and motion tracking involves acquiring image information, the image information including pixel values that correspond to the pixels, calculating a surface quality (SQUAL) value from the image information, determining a level of saturation of the pixel array from pixel values of the image information, comparing the determined level of saturation of the pixel array to a saturation threshold, increasing a SQUAL threshold if the determined level of saturation of the pixel array is greater than the saturation threshold, and deciding whether or not to output motion tracking information in response to a comparison of the SQUAL value to the SQUAL threshold. Other embodiments of the method are also described.