Oxide Semiconductor Transistors for Optical Touch Sensing
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Solution Overview
Problem
Conventional optical touch screen apparatuses face challenges with increased size due to insufficient light sensing capabilities, particularly with amorphous silicon thin-film transistors, which result in delayed sensing times and increased parasitic capacitance.
Innovation Solution
The use of oxide semiconductor transistors sensitive to different wavelength bands of light, alternately arranged with light sensing and touch sensing pixels, connected through specific data and reset lines, allows for efficient remote and touch sensing by distinguishing between external light and display light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If amorphous silicon thin-film transistors are used for light sensing, then the optical touch screen can be implemented, but the sensing time is delayed due to charge accumulation in capacitor
Solution Approach 1:
The patent changes the material parameter of the transistor from amorphous silicon to oxide semiconductor, which fundamentally alters the charge transport properties. This material substitution eliminates the need for charge accumulation in capacitors, thereby reducing sensing time while maintaining reliable light detection capability through the inherent properties of oxide semiconductor transistors.
Solution Approach 2:
The invention extracts and removes the capacitor component from the pixel structure. By using oxide semiconductor transistors that can directly sense light without requiring charge accumulation, the patent eliminates the capacitor that was previously necessary for storing charges, thereby removing the time delay associated with charge accumulation and discharge cycles.
2Area of stationary object
If the size of optical touch screen apparatus increases, then more sensing elements are needed, but parasitic capacitance increases
Solution Approach 1:
The patent changes the electrical parameters of the transistor by substituting amorphous silicon with oxide semiconductor material. This material change results in lower off-state current and reduced parasitic capacitance, allowing the display size to increase without proportionally increasing parasitic capacitance and device complexity.
3Adaptability or versatility
If light sensing pixels and touch sensing pixels are integrated, then remote sensing and touch sensing can be performed, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by enabling oxide semiconductor transistors to perform both light sensing and touch sensing functions within the same pixel structure. By sensing different wavelength bands (visible light for touch, infrared for remote sensing), the same transistor serves multiple purposes, reducing overall device complexity while maintaining versatile sensing capabilities.
Solution Approach 2:
The invention applies local quality differentiation by assigning different wavelength sensing capabilities to different regions or configurations of the oxide semiconductor transistor. The transistor can be configured to sense specific wavelength bands locally, allowing simultaneous touch sensing (visible light) and remote sensing (infrared) without requiring completely separate pixel structures.
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 configuration enhances the sensitivity and accuracy of optical touch screen apparatuses, enabling effective remote sensing and touch input across various distances without the need for direct contact, while reducing parasitic capacitance and improving response times.
Implementation Method 1
oxide semiconductor transistors sensitive to different wavelength bands of light
Data Source
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Figure 5~6A
AI summary
Optical touch screen apparatuses with remote sensing and touch sensing by using a light sensor transistor including an oxide semiconductor transistor. The optical touch screen apparatus includes a pixel array of a plurality of sensing pixels arranged in a plurality of rows and a plurality of columns. Each of the sensing pixels includes a light sensing pixel for sensing light that is irradiated by an external light source and a touch sensing pixel for sensing display light that is reflected by a screen touch. The light sensing pixel includes a first light sensor transistor and a first switch transistor connected each other in series, and the touch sensing pixel includes a second light sensor transistor and a second switch transistor connected each other in series.