Capacitive Touch Sensor Circuit for Distance Detection in Thin Displays
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Solution Overview
Problem
Existing capacitance-type touch sensors for liquid crystal display devices face challenges in detecting objects at a distance, leading to increased thickness and difficulty in integrating circuits, particularly in mobile device applications, where user potential is often unfixed and space-saving is crucial.
Innovation Solution
A capacitance-type touch sensor design that includes drive electrodes and detection electrodes forming capacitance, with a detection circuit and controller to change the range of electric flux lines, allowing for object detection both in contact and at a distance by using the common electrode as both a display and sensor drive electrode with a higher voltage signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is added to prevent scratches on the touch sensor, then the durability and reliability of the touch sensor is improved, but the total thickness of the liquid crystal module increases
Solution Approach 1:
The patent combines the protective layer function with the touch sensor structure by making the outer surface of the polarizing plate serve as both the touch surface and protective surface. The conductive film is formed between the observation-side substrate and the polarizing plate, eliminating the need for separate protective layers while maintaining scratch resistance through the inherent durability of the polarizing plate surface.
Solution Approach 2:
The polarizing plate is designed to serve multiple functions simultaneously: it acts as the touch sensor surface, provides scratch protection, and maintains its optical polarization function. This multi-functionality eliminates the need for additional dedicated protective layers, thereby preventing thickness increase while ensuring durability.
2Length of stationary object
If the conductive film for touch sensor is positioned between the observation-side substrate and polarizing plate, then the thickness is reduced, but the user potential must be fixed and secure grounding is required
Solution Approach 1:
The patent changes the electrical parameters of the touch sensor system by using the outer surface of the polarizing plate as the touch surface instead of requiring a separate conductive layer. This configuration allows the touch sensor to operate with unfixed user potential, as the capacitance detection is performed through the polarizing plate surface which can accommodate varying potential conditions without requiring secure grounding.
3Reliability
If separate circuit portions are provided for touch sensor drive and coordinate detection, then the touch sensor functionality is improved, but the overall circuit integration becomes difficult
Solution Approach 1:
The patent merges the touch sensor drive circuit and coordinate detection circuit into a single integrated circuit unit. The detection circuit is designed to perform both the driving of the conductive film and the detection of touch coordinates simultaneously, eliminating the need for separate circuit portions and achieving full integration on the liquid crystal display element.
Solution Approach 2:
The integrated circuit is designed to perform multiple functions: it drives the conductive film, detects touch events, and determines touch coordinates all through a single circuit architecture. This multi-functional design simplifies the overall device structure and achieves high-level integration while maintaining accurate touch detection capability.
4Device complexity
If the capacitance-type touch sensor uses the common electrode for display drive, then the circuit integration is improved, but the detection range is limited to contact or close approach
Solution Approach 1:
The patent extends the detection capability from only contact or close approach to long-distance detection by utilizing the electric flux lines that extend beyond the immediate vicinity of the common electrode. The detection circuit is designed to sense capacitance changes caused by objects at a distance, effectively adding a spatial dimension to the detection range while maintaining circuit integration.
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
Enables detection of objects at a distance and improves detection sensitivity, allowing for integrated display and sensor circuits on a single board, suitable for mobile devices by reducing thickness and enhancing user interaction.
Implementation Method 1
one or more detection electrodes forming capacitance in cooperation with the respective drive electrodes
Implementation Method 2
a controller controlling to change a range of electric flux lines generated between the drive electrodes and the detection electrodes
Data Source
AI summary
A touch sensor that may detect an object away from the sensor is provided. The touch sensor includes one or more drive electrodes; one or more detection electrodes forming capacitance in cooperation with the respective drive electrodes; a detection circuit applying drive signals to the respective drive electrodes to detect the object based on detection signals obtained from the respective detection electrodes in response to the respective drive signals; and a controller controlling to change a range of electric flux lines generated between the drive electrodes and the detection electrodes.