Touch Panel Scan Method for Noise Filtering and Frame Rate
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Solution Overview
Problem
Capacitive touch panels face interference from AC and LCM noises, leading to degraded accuracy in recognizing touch objects due to the difficulty in distinguishing between noise and touch signals based on capacitance variation values.
Innovation Solution
A mutual scan method that involves receiving a self-sensing frame, calculating and marking sensing slopes, and executing a mutual scan only on marked lines to exclude noise sensing points, thereby increasing the frame rate by reducing unnecessary driving lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensing threshold is decreased to recognize low sensitivity touch signals (stylus), then noise sensing signals are incorrectly recognized as touch objects, but if the sensing threshold is increased to exclude noise, then low sensitivity touch signals cannot be recognized
Solution Approach 1:
The patent segments the sensing lines into two groups: marked sensing lines (where slope > threshold) and unmarked sensing lines. Mutual scan is performed only on marked sensing lines, while unmarked lines are excluded. This segmentation allows the system to focus computational resources on lines with actual touch signals while filtering out noise, resolving the contradiction between recognizing low-sensitivity touches and excluding noise.
Solution Approach 2:
The patent performs a preliminary self-scan to calculate sensing slopes for all sensing lines before executing the mutual scan. This preliminary action identifies which sensing lines have actual touch signals (slope > threshold) versus noise (slope ≤ threshold), allowing the subsequent mutual scan to be performed only on relevant lines, thereby improving both accuracy and frame rate.
2Measurement precision
If mutual scan is performed on all sensing lines, then complete coverage is achieved, but the frame rate is reduced due to processing time
Solution Approach 1:
The patent applies partial action by performing mutual scan only on marked sensing lines (those with slope > threshold) rather than all sensing lines. Since noise signals have slope ≤ threshold, they are excluded from mutual scan processing. This partial processing maintains sensing coverage for actual touch objects while significantly improving frame rate by reducing unnecessary computations on noise-containing lines.
3Productivity
If the sensing threshold is set to recognize stylus touches, then frame rate decreases due to processing all lines, but if processed selectively, then noise filtering improves accuracy
Solution Approach 1:
The patent performs a preliminary self-scan to calculate sensing slopes for all sensing lines before executing the mutual scan. This preliminary action identifies which sensing lines have actual touch signals (slope > threshold) versus noise (slope ≤ threshold), allowing the subsequent mutual scan to be performed only on relevant lines, thereby improving both accuracy and frame rate.
Solution Approach 2:
The patent segments the sensing lines into two groups: marked sensing lines (where slope > threshold) and unmarked sensing lines. Mutual scan is performed only on marked sensing lines, while unmarked lines are excluded. This segmentation allows the system to focus computational resources on lines with actual touch signals while filtering out noise, resolving the contradiction between recognizing low-sensitivity touches and excluding noise.
Data Source
AI summary
A scan method for a touch panel has steps of: receiving a self-sensing frame; calculating sensing slopes between each sensing line and its neighboring sensing lines in the self-sensing frame; determining whether any sensing slope is larger than a slope threshold, and marking the sensing line if the sensing slope is larger than the slope threshold; and executing a mutual scan approach on the marked sensing lines to produce a mutual sensing frame without sensing point caused by noise. Further, the present invention also increases the frame rate since only a part of sensing lines need to be scanned.