Display Device Touch Detection Using Capacitive Coupling and Optical Input
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Solution Overview
Problem
Conventional display devices with optical input functions face challenges in accurately determining whether an object is touching the screen, especially under ambient lighting conditions, leading to incorrect inputs due to difficulties in distinguishing between a finger touching the screen and one in the air.
Innovation Solution
A display device incorporating a capacitive coupling detector and an optical input unit that uses a processor to determine touch coordinates by analyzing capacitive coupling and image data from a capacitive coupling detector and optical sensor, with a sensor capacitance element connected in parallel to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical input function is used to detect touch by picking up images, then the display device can detect object proximity, but accuracy in determining whether object actually touches the screen deteriorates under ambient lighting conditions
Solution Approach 1:
The patent combines optical input unit and capacitive coupling detector into a single display device, merging image-based proximity detection with capacitance-based contact detection. This integration allows the system to leverage both detection methods simultaneously, using optical data for preliminary object identification and capacitive data for accurate contact verification, thereby resolving the contradiction between versatility and measurement precision.
Solution Approach 2:
The capacitive coupling detector acts as an intermediary verification mechanism between the optical input unit and the touch processing system. While the optical unit provides initial detection, the capacitive detector serves as a mediator that confirms actual physical contact by measuring changes in capacitance, filtering out false positives from ambient lighting conditions.
2Device complexity
If only optical sensing is used to detect touch, then the device structure remains simple, but reliability of touch input deteriorates due to inability to distinguish between air proximity and actual contact
Solution Approach 1:
The display device achieves multi-functionality by enabling the same sensor system to perform both optical image pickup for proximity detection and capacitive coupling detection for contact verification. The sensor capacitance element serves dual purposes: it is part of the optical sensing system while simultaneously functioning as a capacitive touch sensor, thereby improving reliability without proportionally increasing device complexity.
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
Enhances the accuracy of determining touch timing and coordinates by detecting changes in potential difference across the sensor capacitance element, allowing for precise identification of screen contacts and reducing incorrect inputs.
Implementation Method 1
a capacitive coupling detector, which detects a capacitive coupling to the object adjacent to the display screen
Implementation Method 2
The capacitive coupling detector includes a sensor capacitance element. The power supply unit applies a precharge voltage and a reference voltage respectively to two electrodes of the sensor capacitance element. Here, the precharge voltage and the reference voltage have voltage values oscillating in the same phase. The capacitive coupling detector detects the capacitive coupling according to a change in the potential difference across the precharged sensor capacitance element.
Implementation Method 3
an optical input unit, which picks up an image of an object adjacent to the display screen
Data Source
AI summary
In order to improve accuracy in determining whether or not an object touches a display screen, a display device includes a display unit and a processor. The display unit includes an image display unit which displays an image on a display screen, an optical input unit which picks up an image of an object adjacent to the display screen and a capacitive coupling detector which detects a capacitive coupling to the object adjacent to the display screen. The processor determines that the object touches the display screen by using, and concurrently calculates the coordinates touched by the object by using the capacitive coupling detected by the capacitive coupling detector, and the image picked up by the optical input unit.