Large-Area Capacitive Active Touch Panel Using the Method of Pulse Overlapping Detection

Tai, Ya‐Hsiang; Chiu, Hao-Lin; Chou, Lu-Sheng

doi:10.1109/jdt.2012.2236882

Cited by 18 publications

(8 citation statements)

References 10 publications

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“…The Al-ITZO TFT was designed to be overlapped as little as possible the sensing electrode in a pixel so as to reduce parasitic capacitance. In our FPS array, the sensing time can be affected by a combination of parasitic resistance and capacitance, which is called RC delay 35 . Therefore, the parasitic components were considered in order to confirm the feasibility of adequate operation speed in our fingerprint sensing system.…”

Section: Resultsmentioning

confidence: 99%

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

Jeon

Lee

et al. 2019

Sci Rep

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The fingerprint recognition has been widely used for biometrics in mobile devices. Existing fingerprint sensors have already been commercialized in the field of mobile devices using primarily Si-based technologies. Recently, mutual-capacitive fingerprint sensors have been developed to lower production costs and expand the range of application using thin-film technologies. However, since the mutual-capacitive method detects the change of mutual capacitance, it has high ratio of parasitic capacitance to ridge-to-valley capacitance, resulting in low sensitivity, compared to the self-capacitive method. In order to demonstrate the self-capacitive fingerprint sensor, a switching device such as a transistor should be integrated in each pixel, which reduces a complexity of electrode configuration and sensing circuits. The oxide thin-film transistor (TFT) can be a good candidate as a switching device for the self-capacitive fingerprint sensor. In this work, we report a systematic approach for self-capacitive fingerprint sensor integrating Al-InSnZnO TFTs with field-effect mobility higher than 30 cm 2 /Vs, which enable isolation between pixels, by employing industry-friendly process methods. The fingerprint sensors are designed to reduce parasitic resistance and capacitance in terms of the entire system. The excellent uniformity and low leakage current (<10 −12 ) of the oxide TFTs allow successful capture of a fingerprint image.

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Section: Resultsmentioning

confidence: 99%

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

Jeon

Lee

et al. 2019

Sci Rep

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“…Photo detection touch panel determines the touch signal by using the light reflection or absorption. This method, which is sensitive to the ambient light, easily causes sensing noise [14]. The resistive touch sensors have the advantage of low cost.…”

Section: Introductionmentioning

confidence: 99%

Design of AM Self-Capacitive Transparent Touch Panel Based on a-IGZO Thin-Film Transistors

Zhang

et al. 2020

IEEE Access

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In this work, we propose a novel active-matrix self-capacitance touch panel circuit. Each touch pixel contains only one thin film transistor. The principle of the touch event detection is to detect the voltage change, which is caused by the change of electrode capacitance. The voltage sensing by capacitance sensor is converted to capacitive digital data which compare with default value to judge whether the touch event is touched or not. The simplest structure increase maximizes the sensing pad area and reduce the parasitic effects. An array of 5 × 5 capacitive sensing active-matrix self-capacitive touch panel based on the proposed solution is designed and implemented. The potential for high precision and high reliability is proven in the measurement results.INDEX TERMS Touch panel, thin film transistor, high precision, high reliability.

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“…On the other hand, even though capacitive touch sensing has become one of the most important and popular technology for human-computer interaction, its large area application still suffers from technical obstacles in passive electrode matrix like environment noise, high material resistance, etc. Although some concept of capacitive sensing with TFTs in pixel has been proposed [7], the output voltage difference between touched / untouched state (ǻV) still remains small, or the system is with relatively slow response speed.…”

Section: Introductionmentioning

confidence: 99%

32-2: High-Speed Capacitive Touch Sensor with Pseudo-CMOS Buffer using a-IGZO TFTs on Plastic

Chen

Geng

Jang

2016

SID Symposium Digest of Technical Papers

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We propose a capacitive touch sensor with a-IGZO TFTs on plastic using pseudo-CMOS inverter as output buffer. Benefit from the pseudo-CMOS structure, the sensor achieves both high-speed and large output swing between touched/untouched state. This result demonstrates a novel approach to large area flexible touch sensing applications. Author KeywordsOxide thin-film transistor (TFT), capacitive touch, pseudo-CMOS. BackgroundAdvantages of a-IGZO TFT with high mobility, low temperature process, and scalability [1] resulting in a broadened possibility of large area flat panel displays. And combination of oxide TFTs and flexible substrate [2] has become a major candidate for future flexible electronics. The presented AMOLED pixel circuits [3], gate drivers [4], and other integrated circuits [5] show the potential of using a-IGZO TFTs to achieve panels with more integrated functions. Recently, we proposed high-speed circuits using pseudo-CMOS structure and bulk-accumulation a-IGZO TFTs [6], which can be a good approach to high performance integrated circuits on panel.On the other hand, even though capacitive touch sensing has become one of the most important and popular technology for human-computer interaction, its large area application still suffers from technical obstacles in passive electrode matrix like environment noise, high material resistance, etc. Although some concept of capacitive sensing with TFTs in pixel has been proposed [7], the output voltage difference between touched / untouched state (ǻV) still remains small, or the system is with relatively slow response speed.In this work, we propose a capacitive touch sensor using a-IGZO on flexible substrate. By using the pseudo-CMOS buffer, the circuit shows potential of working under high refresh rate up to 500 kHz with large output ǻV, which makes it robust to be applied to large area touch sensing applications. Experiments TFT FabricationAmorphous IGZO TFTs using back channel etch (BCE) and dual-gate (DG) structure have been fabricated. The proposed flexible substrate is a spin-coated polyimide thin film on a detachable glass [8]. Fig. 1(a) shows the cross sectional view of the TFT structure. Details of the TFT process flow are described elsewhere [9]. Fig. 1 (b) and (c) shows the transfer and output curve of the fabricated TFT, respectively. The TFT has a turn on voltage close to 0V and mobility up to 12 cm 2 /Vs. In order to analyze the speed of the fabricated DG TFTs on plastic, a 7-stage pseudo-CMOS ring oscillator has also been fabricated, as shown in Fig. 2(a). When given a supply voltage of 20V, the ring oscillator exhibits a high oscillating speed of 2.9MHz, as shown in Fig. 2(b), corresponding to a propagation delay of 25ns per stage.This result further proves the potential of DG TFTs and pseudo-CMOS structure to be applied to high-speed circuit designs. Touch Sensor DesignThe circuit diagram of the proposed capacitive touch sensor is shown in Fig. 3(a). The circuit consists of two parts. First part is targeting to transfer the variation of ...

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Large-Area Capacitive Active Touch Panel Using the Method of Pulse Overlapping Detection

Cited by 18 publications

References 10 publications

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

Highly Sensitive Active-Matrix Driven Self-Capacitive Fingerprint Sensor based on Oxide Thin Film Transistor

Design of AM Self-Capacitive Transparent Touch Panel Based on a-IGZO Thin-Film Transistors

32-2: High-Speed Capacitive Touch Sensor with Pseudo-CMOS Buffer using a-IGZO TFTs on Plastic

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