Oxide Semiconductor Transistor Optical Touch Screen
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Solution Overview
Problem
Optical touch screens face challenges with increasing size due to insufficient light current variation in amorphous silicon thin film transistors, leading to parasitic capacitance issues that affect light intensity signal generation.
Innovation Solution
Employing oxide semiconductor transistors, specifically using ZnO or alloys like TaZnO, InZnO, and GalnZnO, as light sensing devices in conjunction with switching transistors, and utilizing a gate driver and reset signal to manage light sensing pixels in a matrix configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amorphous silicon thin film transistors are used as light sensing devices, then the optical touch screen can be implemented, but the variation in current caused by light is not sufficiently large leading to insufficient light sensing accuracy
Solution Approach 1:
The patent changes the material parameter of the transistor from amorphous silicon to oxide semiconductor, which fundamentally alters the electrical characteristics and enables sufficient current variation in response to light, thereby resolving the insufficient light sensing accuracy problem
Solution Approach 2:
The patent employs oxide semiconductor materials (such as In-Ga-Zn-O) that combine multiple metallic elements to achieve superior electrical properties compared to single-material amorphous silicon, enabling both high light sensing accuracy and reliable current variation
2Measurement precision
If charges are accumulated in a capacitor for a predetermined period to generate light intensity signals, then light sensing is achieved, but parasitic capacitance increases as the size of the optical touch screen increases
Solution Approach 1:
The patent extracts and eliminates the capacitor component from the pixel structure by using oxide semiconductor transistors with inherent charge accumulation capability, thereby removing the source of parasitic capacitance while maintaining light intensity signal generation function
Solution Approach 2:
The oxide semiconductor transistor serves multiple functions simultaneously: it acts as both the light sensing element and the charge storage element, eliminating the need for a separate capacitor and reducing device complexity and parasitic capacitance
3Area of stationary object
If the size of display devices is increased to improve visibility, then the display area is enlarged, but the distance between user and display device increases making direct touching difficult
Solution Approach 1:
The patent replaces the mechanical direct-touch system with an optical sensing system that detects light reflected from or emitted by the user's finger, enabling touch functionality on large displays without requiring physical contact
4Measurement precision
If oxide semiconductor transistors are used as light sensing devices, then light sensing accuracy is enhanced and parasitic capacitance is reduced, but the device structure becomes more complex
Solution Approach 1:
The patent merges the light sensing function and charge storage function into a single oxide semiconductor transistor structure, eliminating the need for separate capacitor and reducing overall device complexity despite the advanced material requirements
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 solution enhances light sensing accuracy and reduces parasitic capacitance, enabling efficient light signal processing and improved performance in larger optical touch screens with increased driving speed and reduced power consumption.
Implementation Method 1
a light sensing transistor for sensing light and a switching transistor for outputting a light sensing signal from the light sensing transistor
Data Source
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AI summary
An optical touch screen apparatus in which an oxide semiconductor transistor is used as a light sensing device, and a method of driving the optical touch screen apparatus. The optical touch screen apparatus includes an array including a plurality of light sensing pixels for sensing incident light, a gate driver for providing each of the light sensing pixels with a gate voltage and a reset signal and a signal output unit for receiving a light sensing signal from each of the plurality of light sensing pixels to output a data signal. The gate driver includes a plurality of gate lines that provide a gate voltage to each of the light sensing pixels and at least one reset line that provides a reset signal to each of the light sensing pixels and is electrically connected to the plurality of light sensing pixels.