Oxide Semiconductor Light Sensing Circuit for Optical Touch Screens
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Solution Overview
Problem
Conventional light sensing devices, such as those using amorphous silicon thin film transistors, face challenges in sensing light efficiently due to insufficient current change and delayed sensing times, especially as the size of optical touch screen devices increases, leading to issues with parasitic capacitance and complex circuit requirements.
Innovation Solution
A light sensing circuit utilizing an oxide semiconductor transistor with a channel layer made from materials like ZnO, InO, or InZnO, which operates as both a light sensing device and a switch, allowing for improved light sensitivity and simplified circuitry by using a gate driver to apply specific voltage thresholds to manage light sensing and data output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous silicon thin film transistor is used as light sensing device, then device structure is established, but current change is insufficient and sensing time is delayed
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor (such as IGZO - indium gallium zinc oxide), which fundamentally alters the electrical characteristics including carrier mobility and response time, thereby achieving both sufficient current change and fast sensing speed
Solution Approach 2:
The patent uses composite material structure combining oxide semiconductor channel layer with specific gate electrode materials and insulating layers, creating a multi-layer composite transistor structure that optimizes both sensing capability and response speed
2Measurement precision
If capacitor is used to accumulate electric charges, then light intensity signal can be generated, but sensing time is delayed due to charge accumulation period
Solution Approach 1:
The patent extracts and removes the capacitor component from the pixel structure, relying instead on the oxide semiconductor transistor's inherent ability to generate sufficient current change directly in response to light, thereby eliminating the charge accumulation delay
Solution Approach 2:
The oxide semiconductor transistor serves dual functions as both the light sensing element and the signal output device, eliminating the need for separate capacitor-based charge accumulation circuitry and achieving self-sufficient light detection
3Area of stationary object
If size of optical touch screen device increases, then display area is enlarged, but parasitic capacitance increases
Solution Approach 1:
The patent changes the transistor material parameters to oxide semiconductor, which has superior electrical characteristics including lower off-state current and higher on-off ratio, thereby reducing the impact of parasitic capacitance even as device size increases
Solution Approach 2:
The patent employs a simplified pixel structure segmented into essential components only (oxide semiconductor transistor with gate, source, and drain), removing redundant elements like capacitors, which reduces overall parasitic capacitance while maintaining large display area
4Reliability
If conventional light sensing circuit is used, then light sensing function is achieved, but circuit structure is complex
Solution Approach 1:
The patent merges the light sensing function and switch function into a single oxide semiconductor transistor, eliminating the need for separate capacitors and multiple transistors, thereby achieving simplified circuit structure while maintaining complete light sensing functionality
Solution Approach 2:
The oxide semiconductor transistor is designed to perform multiple functions simultaneously: light sensing, signal generation, and data output switching, making the circuit structure universal and eliminating the need for separate dedicated components for each function
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
The oxide semiconductor transistor-based light sensing circuit achieves high light sensitivity, reducing the need for capacitors and separate data output circuits, enabling faster drive speeds, lower power consumption, and simplified designs for larger optical touch screen devices.
Implementation Method 1
An oxide semiconductor transistor may have a characteristic of being sensitive to light according to a material for an oxide semiconductor that is used as a channel layer
Data Source
AI summary
In a simplified light sensing circuit, a light sensing apparatus including the light sensing circuit, a method of driving the light sensing apparatus, and an image acquisition apparatus and optical touch screen apparatus including the light sensing apparatus, the light sensing circuit includes an oxide semiconductor transistor including a channel layer including an oxide semiconductor material, for each pixel. The oxide semiconductor transistor is configured to operate as a light sensing device that senses light and a switch that outputs light sensing data.