Force Detection Accuracy in Touch Displays via Temperature Compensation
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Solution Overview
Problem
Display apparatuses with touch detection functions face accuracy issues in force detection due to temperature-induced changes in electrostatic capacitance caused by materials like acrylic resin in the backlight layer, leading to erroneous force detection values.
Innovation Solution
Incorporating a force detection controller that corrects force detection values based on a reference capacitance value at a reference temperature, using a ratio between the reference capacitance and the actual capacitance in a non-contact state, to account for temperature-related changes in the dielectric materials within the display apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a layered body made of acrylic resin is provided between the first and second conductors in the backlight device, then the display apparatus can achieve proper backlight functionality, but the electrostatic capacitance between the first and second conductors changes with temperature, reducing force detection accuracy
Solution Approach 1:
The patent introduces a temperature compensation capacitor as an intermediary element that compensates for the temperature-induced capacitance changes in the acrylic resin layered body. This separate capacitor is electrically connected in parallel to the force detection capacitor, and its capacitance value is adjusted to offset the temperature effects, thereby maintaining stable force detection accuracy while allowing the acrylic resin layered body to function properly for backlight illumination.
Solution Approach 2:
The patent changes the electrical parameter (capacitance value) of the temperature compensation capacitor to counteract the temperature-induced changes in the acrylic resin layered body. By adjusting the capacitance value of the compensation capacitor based on temperature information, the system maintains stable electrostatic capacitance measurements for force detection despite temperature variations affecting the backlight components.
2Measurement precision
If the electrostatic capacitance between the first and second conductors is used for force detection, then force detection function is achieved, but temperature variations cause erroneous determination of contact or proximity
Solution Approach 1:
The temperature compensation capacitor serves as a mediator that isolates the force detection system from temperature-induced errors. By providing a parallel capacitance path that compensates for temperature effects, it allows the system to reliably distinguish between actual contact events and temperature-induced capacitance changes, improving both force detection capability and contact determination accuracy.
Solution Approach 2:
The system uses temperature information as feedback to adjust the capacitance value of the temperature compensation capacitor. This feedback mechanism allows the system to continuously compensate for temperature variations, ensuring reliable force detection and contact determination even under changing temperature 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
This approach enhances the accuracy of force detection by mitigating the effects of temperature variations, ensuring precise force measurement regardless of temperature changes in the display apparatus.
Implementation Method 1
detect contact with or proximity to the input surface by the detection target object based on electrostatic capacitance between the first electrode and the touch detection electrode
Implementation Method 2
detect a force applied to the input surface by the detection target object based on electrostatic capacitance between the first electrode and the second electrode
Implementation Method 3
Such an acrylic resin expands or contracts with changes in temperature. Consequently, the electrostatic capacitance between the first and second conductors changes
Data Source
AI summary
According to an aspect, a display apparatus with a touch detection function, the display apparatus includes: an input surface; a touch detection electrode; a first electrode; a second electrode facing the first electrode across a dielectric layer; a touch detection controller configured to detect contact with or proximity to the input surface by a detection target object based on electrostatic capacitance between the first electrode and the touch detection electrode; and a force detection controller configured to detect a force applied to the input surface by the detection target object based on electrostatic capacitance between the first electrode and the second electrode. The force detection controller is configured to correct a force detection value based on a reference capacitance value between the first electrode and the second electrode at a reference temperature in a non-contact state of the detection target object with the input surface.