Photoelectric Sensor Signal Amplification for Touch Detection Noise Reduction
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Solution Overview
Problem
Existing photoelectric sensors in TFT-LCD displays face issues with leakage currents due to photocurrent generation under varying light intensities, leading to noise interference and reduced accuracy in touch detection.
Innovation Solution
A photoelectric sensor design comprising a photoelectric element, amplifying transistor, readout transistor, reset transistor, and capacitor, with specific terminal connections and voltage levels, amplifies electric signals and improves signal-to-noise ratio through controlled signal phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a-Si TFT channel is shaded from light to reduce leakage current, then leakage current is reduced, but manufacturing complexity increases due to additional shielding structures
Solution Approach 1:
The patent converts the harmful photocurrent effect into a beneficial feature by using the light-sensitive property of a-Si TFT to detect touch events. Instead of blocking light with additional shielding structures, the invention utilizes the photocurrent generated by light exposure as the detection mechanism, thereby eliminating the need for complex shielding while maintaining low leakage current performance.
Solution Approach 2:
The a-Si TFT serves dual functions: as a switching transistor for display control and as a photoelectric sensor for touch detection. This multi-functionality eliminates the need for separate shielding structures and dedicated touch sensing components, reducing overall device complexity while maintaining reliable low leakage current characteristics.
2Use of energy by moving object
If readout TFTs are kept off to reduce power consumption, then power consumption is reduced, but leakage currents from other readout TFTs create noise that reduces detection accuracy
Solution Approach 1:
The patent divides the readout operation into distinct time segments: a reset phase where all readout TFTs are turned on to establish reference levels, and a detection phase where only the specific readout TFT corresponding to the touched pixel is activated. This temporal segmentation allows power consumption to be minimized while eliminating noise from other readout TFTs during the critical detection phase, thereby maintaining high touch detection accuracy.
Solution Approach 2:
The readout operation follows a periodic cycle: first, all readout TFTs are briefly activated to reset capacitors and establish baseline voltage levels; then, only the required readout TFT is activated for signal reading. This periodic activation pattern reduces overall power consumption while ensuring that noise from other readout TFTs does not interfere with detection accuracy during the active reading phase.
3Adaptability or versatility
If photocurrent is utilized for photoelectric conversion to enable integrated optical touch screen, then integration is achieved, but leakage current varies with light intensity causing detection noise
Solution Approach 1:
The patent applies a preliminary reset action before each touch detection event. A reset signal is applied to all photoelectric sensors to clear accumulated charges and establish a known reference voltage level on the capacitors. This preliminary action eliminates the influence of varying light intensity on the detection baseline, allowing accurate touch detection to be performed by measuring voltage changes from this established reference point, thereby maintaining high precision while enabling integrated optical touch screen functionality.
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 enhances the precision of photoelectric detection by amplifying readout signals and reducing noise, facilitating accurate touch detection in TFT-LCD displays.
Implementation Method 1
a photoelectric element, an amplifying transistor, a readout transistor, a reset transistor and a capacitor... the photoelectric element comprises an output terminal and a reference level input terminal
Data Source
AI summary
The present disclosure provides a photoelectric sensor and driving method thereof, as well as an array substrate and a display device. The photoelectric sensor comprises a photoelectric element having an output terminal and a reference level input terminal, an amplifying transistor, a readout transistor, a reset transistor, a capacitor and a plurality of control input terminals. The output terminal of the photoelectric element, the gate of the amplifying transistor and the source of the reset transistor are connected to a first terminal of the capacitor. The reference level input terminal, the sources of the readout transistor and amplifying transistor are connected to a first reference voltage input terminal. The drains of the reset transistor and amplifying transistor are connected to a second reference voltage input terminal. The gates of the read-out transistor and reset transistor are respectively connected to a control input terminal.