High Granularity Resistive Touchscreen Eliminating Interconnect Inaccuracies
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Solution Overview
Problem
Existing digital resistive touchscreen designs face limitations in touch detection precision and accuracy due to large touchells and the use of silver epoxy traces, which increase resistance and complicate data processing, leading to slow scan times and reduced resolution.
Innovation Solution
The touchscreen device employs smaller touchells of 3.175 mm by 3.175 mm and eliminates silver epoxy interconnects, utilizing an integrated circuit for digital scan-based touch detection and communication via a serial bus, allowing for multiple touchscreens with distinct touchell networks or divided quadrants to enhance precision and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If large touchells (12.7 mm x 12.7 mm) are used to limit the number of interconnect traces, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent divides the touchscreen into multiple smaller touchell regions (e.g., 3.175 mm x 3.175 mm or 6.35 mm x 6.35 mm) instead of using fewer large touchells. This segmentation increases the number of measurement points across the screen, improving touch detection precision while managing interconnect complexity through reduced trace lengths per touchell.
2Ease of manufacture
If silver epoxy traces are used for interconnect, then ease of manufacture is improved, but measurement precision deteriorates due to added resistance
Solution Approach 1:
The patent removes silver epoxy traces from the measurement path entirely by implementing a fully digital scanning architecture. The ITO tracks are scanned using digital voltage levels, and touch detection is performed through digital comparison circuits, eliminating the parasitic resistance introduced by silver epoxy interconnects in analog measurement paths.
Solution Approach 2:
The patent replaces the analog measurement system with silver epoxy traces with a digital scanning system. Instead of using continuous analog voltage measurements through resistive traces, the system applies digital voltage levels and detects touches through digital comparison, substituting analog electrical measurement with digital electrical measurement to eliminate trace resistance effects.
3Speed
If digital scan is used for touch detection, then scan speed is improved, but measurement precision deteriorates compared to analog scan
Solution Approach 1:
The patent uses multiple smaller touchell regions arranged in a grid pattern to compensate for the coarser granularity of digital scanning. By having more discrete measurement points across the screen surface, the system achieves high-resolution positional data through the increased spatial sampling provided by the segmented touchell structure, even though each individual touchell is scanned digitally rather than measured analogously.
Data Source
AI summary
A touchscreen device utilizes digital scan to resolve a touch location with high precision. The touchscreen device includes touchells of about 3.175 mm by 3.175 mm (0.125 inches by 0.125 inches). An integrated circuit detects contacts in the touchells that resolve to touches on the touchscreen, and communicates those touches to a micro-controller via a serial bus. Silver epoxy interconnects for the tracks are reduced or eliminated. Multiple touchscreens having distinct touchell networks may be disposed to create a larger touchscreen area. Similarly, a single touchscreen may be divided quadrants, each with a distinct touchell network.