Height-Dependent Filter for Digitizer Jitter Reduction
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Solution Overview
Problem
Pointing devices, such as digitizer tablets, suffer from jitter instability in coordinate measurements due to external noise interference, which is not effectively addressed by existing low-pass filtering methods that can introduce filtering artifacts and distort valid user input data.
Innovation Solution
A method and apparatus that adjust filter parameters based on the tool's height above the tablet surface to minimize jitter, using a height-dependent filter that estimates jitter from the signal-to-noise ratio and adjusts the filter depth to balance jitter reduction with preservation of high-frequency content representing user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter is applied to reduce jitter in coordinate position signals, then jitter is reduced, but filtering artifacts are introduced that remove valid high-frequency user input data
Solution Approach 1:
The filter parameters are made dynamic rather than static, allowing the filter to adapt its characteristics based on real-time conditions. The system continuously monitors the difference between consecutive coordinate positions and adjusts the filter strength accordingly, applying stronger filtering when positions are stable and weaker filtering when rapid changes occur, thus preserving valid user input while reducing jitter.
Solution Approach 2:
The filter parameters (such as cutoff frequency or filter coefficient) are changed based on the detected conditions. When the system detects large coordinate changes exceeding a threshold, it modifies the filter parameters to reduce filtering strength, thereby preserving high-frequency valid input data while still maintaining jitter reduction during stable periods.
2Stability of the object's composition
If a strong low-pass filter is used to eliminate jitter, then coordinate stability is improved, but the response time to valid user input decreases
Solution Approach 1:
The filter dynamically adjusts its strength based on the detected motion characteristics. During periods of rapid coordinate change indicating valid user input, the filter automatically reduces its strength to maintain responsive tracking. During periods of stability, the filter increases strength to eliminate jitter, thus achieving both stability and speed at different times as needed.
Solution Approach 2:
The system uses feedback from consecutive position measurements to control the filter behavior. By comparing current position with previous positions and detecting when changes exceed a threshold, the system creates a feedback loop that adjusts filter parameters in real-time, ensuring the filter responds appropriately to actual user input rather than treating all changes as noise.
Data Source
AI summary
A height dependent filter for a pointing device or digitizer tablet, a method of reducing jitter in position data of a pointing device, and a computer readable medium are provided. A method of stabilizing positional data in a digitizer tablet associated with a display device for reporting a position of a pointer includes detecting a current location of the pointer with respect to a coordinate grid defined on the tablet and outputting a position signal indicative of the current pointer location. Noise is filtered from the position signal based on at least one filter parameter. A distance between the pointer and a point on the tablet is determined, and an amount of jitter in the position signal is determined based on the determined distance. The at least one filter parameter is adjusted based on the estimated amount of jitter.