Oxide Semiconductor Light Sensing Circuit for Thin Optical Touch Panels
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Solution Overview
Problem
Current touch panels, particularly resistive overlay touch panels, face challenges with durability and usability at larger distances due to external pressure damage and require complex light sensing circuits with large parasitic capacitance, making it difficult to manufacture large optical touch panels.
Innovation Solution
A light sensing circuit using an oxide semiconductor transistor as a light sensing element, integrated with a switch transistor and a light shielding film on a substrate, simplifies the structure and manufacturing process, allowing for efficient light sensing and data output without the need for additional capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon photodiode is used as the light sensing element, then light sensing function is achieved, but the photocurrent is small requiring additional capacitors that increase circuit complexity and size
Solution Approach 1:
The patent changes the material parameter from silicon to oxide semiconductor, which fundamentally alters the光电 conversion characteristics to produce sufficient photocurrent without requiring additional capacitors for charge accumulation
Solution Approach 2:
The patent extracts and eliminates the capacitor component from the circuit by using oxide semiconductor transistors that inherently generate adequate photocurrent, thereby simplifying the overall circuit structure while maintaining light sensing functionality
2Reliability
If a silicon photodiode is used as the light sensing element, then light sensing function is achieved, but parasitic capacitance increases making it difficult to manufacture large optical touch panels
Solution Approach 1:
The patent changes the material parameter from silicon to oxide semiconductor, which fundamentally alters the光电 conversion characteristics to produce sufficient photocurrent without requiring additional capacitors for charge accumulation
Solution Approach 2:
The patent extracts and eliminates the capacitor component from the circuit by using oxide semiconductor transistors that inherently generate adequate photocurrent, thereby simplifying the overall circuit structure while maintaining light sensing functionality
3Measurement precision
If resistive overlay touch panels are used, then excellent sensing effect is achieved, but the upper or lower conductive layer may be damaged due to external pressure
Solution Approach 1:
The patent replaces the mechanical pressure-based resistive sensing system with an optical sensing system that detects touch through light reflection changes, eliminating the need for vulnerable conductive layers and providing both excellent sensing effect and durability
4Measurement precision
If resistive overlay touch panels are used, then sensing function is achieved, but they can be used only when a distance between the panel and user is small
Solution Approach 1:
The patent replaces the mechanical pressure-based resistive sensing system with an optical sensing system that detects touch through light reflection changes, eliminating the need for vulnerable conductive layers and providing both excellent sensing effect and durability
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 solution enables the creation of thinner, larger optical touch panels and image acquisition apparatuses with improved sensitivity and reduced complexity, enabling precise light sensing and data output, thus overcoming the limitations of existing touch panel technologies.
Implementation Method 1
a light sensor transistor configured to sense light
Implementation Method 2
a light shielding film on a light incident surface of the switch transistor, the light shielding film being configured to substantially block light from being incident on the switch transistor
Data Source
AI summary
A light sensing circuit using an oxide semiconductor transistor, a method of manufacturing the light sensing circuit, and an optical touch panel including the light sensing circuit. Because the light sensing circuit includes only one light sensor transistor and one switch transistor formed on the same substrate, a structure of the light sensing circuit is simplified. Furthermore, because the light sensor transistor and the switch transistor have the same structure, a method of manufacturing the light sensing circuit is also simplified. Also, since an optical touch panel or an image acquisition apparatus using the light sensing circuit uses the light sensing circuit having a simple structure and does not use a capacitor, the optical touch panel or the image acquisition apparatus may be made thinner and larger.