Pixel Voltage Research Articles

Thin-Film Transistor Digital Microfluidics Circuit Design with Capacitance-Based Droplet Sensing.

With the continuous expansion of pixel arrays in digital microfluidics (DMF) chips, precise droplet control has emerged as a critical issue requiring detailed consideration. This paper proposes a novel capacitance-based droplet sensing system for thin-film transistor DMF. The proposed circuit features a distinctive inner and outer dual-pixel electrode structure, integrating droplet driving and sensing functionalities. Discharge occurs exclusively at the inner electrode during droplet sensing, effectively addressing droplet perturbation in existing sensing circuits. The circuit employs a novel fan-shaped structure of thin-film transistors. Simulation results show that it can provide a 48 V pixel voltage and demonstrate a sensing voltage difference of over 10 V between deionized water and silicone oil, illustrating its proficiency in droplet driving and accurate sensing. The stability of threshold voltage drift and temperature was also verified for the circuit. The design is tailored for integration into active matrix electrowetting-on-dielectric (AM-EWOD) chips, offering a novel approach to achieve precise closed-loop control of droplets.

The MIRI/MRS Library. I. Empirically correcting detector charge migration in unresolved sources

The James Webb Space Telescope (JWST) has been collecting scientific data for over two years now. The Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI) has been one of the telescope's most popular modes, and has already produced ground-breaking results. Scientists are now looking deeper into the data for new exciting discoveries, which introduces the need to characterise and correct known systematic effects to reach the photon noise limit. Five important limiting factors for the MRS are the pointing accuracy, non-linearity, detector charge migration, detector scattering---resulting in both spatial broadening and spectral interferometric fringing---the accuracy of the point-spread function (PSF) model, and the complex interplay between these. The Cycle 2 calibration programme 3779, entitled ‘The MIRI/MRS Library', proposed a 72-point intra-pixel dither raster of the calibration star 10-Lac, which provides a unique dataset tailored for the purpose of addressing the limiting factors on the MRS data accuracy. In this first work of the paper series, we aim to address the degeneracy between the non-linearity and charge migration (brighter-fatter effect) that affect the pixel voltage integration ramps of the MRS. Due to the low flux in the longer wavelengths, we only do this in the 4.9 to 11.7 micron region (spectral channels 1 and 2). We fitted the ramps individually per pixel and dither, in order to fold in the deviations from classical non-linearity that are caused by charge migration. The ramp shapes should be repeatable depending on the part of the PSF that is sampled. By doing so, we defined both a grid-based linearity correction, and an interpolated linearity correction. Including the change in ramp shape due to charge migration yields significant improvements compared to the uniform illumination assumption that is currently used by the standard JWST calibration pipeline. The standard deviation on the pixel ramp residual non-linearity is between 70-90<!PCT!> smaller than the current standard pipeline when self-calibrating with the grid. We are able to interpolate these coefficients to apply to any unresolved source not on the grid points, resulting in an up to 70<!PCT!> smaller standard deviation on the residual deviation from linearity. After applying the correction, the full-width at half maximum is up to 20<!PCT!> narrower for sources that cover the full pixel dynamic range. Furthermore, the depth of the fringes is now consistent up the ramp, improving the standard deviation on the difference in fringe depth between the start and ends of integrations by sim 60<!PCT!>. Pointing-specific linearity corrections allow us to accurately model the pixel ramps across the PSF, and for the first time, fix the systematic deviation in the slopes. In this work we demonstrated this for unresolved sources. The discovered trends with PSF sampling suggest that, in the future, we may be able to model ramps for spatially extended and resolved illumination as well.

36.2: ADS Display Mode Gaming TV compatible with G‐Sync

This paper study the impact of pixel voltage leakage and liquid crystal flexoelectric effect on flicker with simulation and measurement method. The impact rule of pixel architecture, TFT voltage, electrode design, liquid crystal material, driving signal and other factors is obtained, and the key factors under different conditions are identified. The pixel design and liquid crystal scheme under different conditions are proposed, and a strategy of data voltage modulation at the blanking stage combined with frequency‐wise ACC brightness compensation is established to reduce flicker. Based on the proposed complete flicker optimization strategy, flicker lower than ‐50dB is achieved on 55/65/75 inch 4K gaming products when switching back and forth at 48/120Hz every 200ms, meeting the G‐Sync flicker standard.

Improving Flicker of Low-Refresh-Rate Driven Active-Matrix Organic Light-Emitting Diode Display

The brightness of low-temperature polycrystalline silicon and metal-oxide (LTPO) active-matrix organic light-emitting diode (AMOLED) display under low-refresh-rate driving condition tends to increase during pixel voltage holding time of each frame even though there is no critical leakage current path from the storage capacitor. We have found that the main cause of the brightness increase is electron trapping into the gate insulator of driving thin film transistor (DTFT) which operates in the saturation mode prone to hot carrier injection. We propose a novel driving method to suppress the brightness variation by applying a high voltage to the source and drain of the DTFT during the non-emitting time which is inserted periodically for dimming the organic light-emitting diode (OLED) display. Our experimental results show that the brightness variation can be reduced from 3.7 % to 1.4 % at the 63rd gray level by the proposed DTFT reset scheme.

Solution for Mass Production of High-Throughput Digital Microfluidic Chip Based on a-Si TFT with In-Pixel Boost Circuit.

As one of the most popular research hotspot of lab-on-chip, digital microfluidic (DMF) technology based on the principle of electrowetting has unique advantages of high-precision, low cost and programmable control. However, due to the limitation of electrodes number, the throughput is hard to further upgrade. Therefore, active matrix electrowetting-on-dielectric (AM-EWOD) technology is a solution to acquire larger scale of driving electrodes. However, the process of manufacturing of AM-EWOD based on thin-film-transistor (TFT) is complex and expensive. Besides, the driving voltage of DMF chip is usually much higher than that of common display products.In this paper, a solution for mass production of AM-EWOD based on amorphous silicon (a-Si) is provided. Samples of 32 × 32 matrix AM-EWOD chips was designed and manufactured. A boost circuit was integrated into the pixel, which can raise the pixel voltage up by about 50%. Customized designed Printed Circuit Board (PCB) was used to supply the timing signals and driving voltage to make the motion of droplets programmable. The process of moving, mixing and generation of droplets was demonstrated.The minimum voltage in need was about 20 V and a velocity of up to 96 mm/s was achieved. Such an DMF device with large-scale matrix and low driving voltage will be very suitable for POCT applications.

P‐16.10: The Introduction of Circuit Simulation Model for TDDI Panels

The multiplexing of common electrode is the frequently used method in TDDI panels now. By this way, common electrode can be used not only as the electrode of Liquid Crystal, but also as touch sensor of TDDI panel. Due to the coupling effect on common electrode from change of pixel voltage, gate and data signal, the change of common electrode may cause unexpected abnormal voltage difference between common and pixel electrode voltage, which may induce different voltage on Liquid Crystal. In this case, there would be inhomogeneous visual effect between adjacent pixels, which may be captured by human eyes in forms of horizontal stripes, gray blocks and some other defects. In order to forecast and prevent the display defects, we explored the circuit‐simulation model to simulate the voltage change of common electrode, which included the influence of gate, data and pixel. Also, the difference of between adjacent pixels is focused to determine whether visual defects would be seen, and based on this result, the design of touch sensor of TDDI panels may be improved.

Design of a Pseudo-Wide Dynamic Range CMOS Image Sensor by Using the Bidirectional Gamma Curvature Technique

This brief presents a $640\times 480$ CMOS image sensor (CIS) with in-circuit bidirectional gamma correction for use in computer vision applications. The conventional gamma correction method can saturate the bright region in an image, leading to the loss of bright image information. Using the proposed bidirectional gamma correction method, which can be implemented with a log-exponential counter, both bright and dark regions in an image can be simultaneously corrected. The transfer function of an 8-bit single-slope analog-to-digital converter can be selected considering either linear or bidirectional gamma curves with three different slope-change points to enhance the visibility in the pseudo-dynamic range. From the prototype sensor, we observed that the visibility of dark images was increased with proper bidirectional gamma curvatures. The CIS was fabricated in a 110 nm CIS process, and the full chip area was 5900 $\mu \text{m}\,\,\mathbf {\times }\,\,5240\,\,\mu \text{m}$ . The total power consumption was 6 mW at a rate of 15 frames per second with an analog, pixel, and digital supply voltage of 3.3 V, 3.3 V, and 1.5 V, respectively.

P‐13.10: AMOLED IR‐drop Automatic Compensation Based on Real ELVDD

This paper introduces a scheme to compensate IR drop in real time based on the real ELVDD in display. The real ELVDD of each row of pixels at the time of charge and discharge is obtained by designing detection circuits on both sides of the display, and the pixel voltage Vdata is adjusted by the detection voltage. In this way, the display problem caused by local and global IR drop can be solved in a direct and effective way.

P‐1.7: Novel Design of Boost Circuit in Pixel

This paper presented a new design of boost circuit in pixel, which could meet the demand for high driving voltage in some special applications and avoid the increasing cost caused by using chips with high‐voltage output. The main circuit of pixel unit contained 3 TFTs and 3 capacitors. Compared with conventional TFT‐LCD, 2 new kinds of signals were added. 1 clock signal was shared by all pixels and 1 additional scanning signal was designed for each row. Through reasonable circuit parameters and timing design, the circuit scheme proposed in this paper could achieve effective boost. The simulation showed the pixel voltage was increased by 60%, compared with the voltage provided by the data line. In the actual sample verification, the voltage was increased by 50%. Therefore, the feasibility of circuit function was verified. Details of design, simulation and verification would be introduced in the text.

Calibration Empowered Minimalistic Multi-Exposure Image Processing Technique for Camera Linear Dynamic Range Extension

Proposed for the first time is a novel calibration empowered minimalistic multi-exposure image processing technique using measured sensor pixel voltage output and exposure time factor limits for robust camera linear dynamic range extension. The technique exploits the best linear response region of an overall nonlinear response image sensor to robustly recover via minimal count multi-exposure image fusion, the true and precise scaled High Dynamic Range (HDR) irradiance map. CMOS sensor-based experiments using a measured Low Dynamic Range (LDR) 44 dB linear region for the technique with a minimum of 2 multi-exposure images provides robust recovery of 78 dB HDR low contrast highly calibrated test targets.

Fully Digital Driving Circuit for TFT LCD Using the Concept of Ramp-Stop

A fully digital driving circuit for thin-film transistor liquid crystal display can offer benefits, including less power consumption and a shortened design schedule. Using the pulsewidth signal to control the moment to stop the ramp voltage, the pixel voltage can be set accurately. In this paper, the possible issues of power consumption, device nonuniformity, and parasitic capacitance are well-studied to prove the feasibility and advantages of the digital driving method. It is prospectively expected to substitute for the conventional analog driving method in the future.

X-ray detection based on complementary metal-oxide-semiconductor sensors

Complementary metal-oxide-semiconductor (CMOS) sensors can convert X-rays into detectable signals; therefore, they are powerful tools in X-ray detection applications. Herein, we explore the physics behind X-ray detection performed using CMOS sensors. X-ray measurements were obtained using a simulated positioner based on a CMOS sensor, while the X-ray energy was modified by changing the voltage, current, and radiation time. A monitoring control unit collected video data of the detected X-rays. The video images were framed and filtered to detect the effective pixel points (radiation spots). The histograms of the images prove there is a linear relationship between the pixel points and X-ray energy. The relationships between the image pixel points, voltage, and current were quantified, and the resultant correlations were observed to obey some physical laws.

Flicker modeling scheme of liquid crystal displays based on current leakage without information about TFT parameters

It is well known that the current leakage at a switching thin film transistor (TFT) of a pixel circuit is one of key factors for the luminance fluctuation of liquid crystal displays (LCDs) perceived as a flicker artifact. This paper proposes a flicker estimation scheme based on the current leakage model of an amorphous silicon (a-Si) TFT. The proposed scheme consists of four blocks such as gray-to-voltage conversion, pixel voltage update, voltage-to-transmittance conversion, and flicker estimation. Gray-to-voltage and voltage-to-transmittance conversion blocks are built from measured data at a source driver and a panel for gray levels. Flicker estimation is established by applying fast Fourier transform (FFT) to simulated transmittance waveforms. The pixel voltage update block is made up by the voltage leakage model which parameters are estimated by matching simulation results to measurement results at a band gray pattern regarding several gray levels. Any given information of TFTs is not required for parameter extraction. The proposed method is applied to a WSXGA+ in-plane switching (IPS) LCD of a 1-dot inversion and flicker levels are estimated within an error range of ±0.6 dB at full gray patterns of gray levels from 32 to 224, compared to measurement results.

A 32 $\times$ 32 ISFET Chemical Sensing Array With Integrated Trapped Charge and Gain Compensation

This paper presents a CMOS-based $32\times 32$ ion-sensitive field-effect transistor (ISFET) system-on-chip for real-time ion imaging. Fabricated in an unmodified 0.35- $\mu \text{m}$ CMOS technology, the ISFET sensor array is based on a pixel topology, which uses capacitive feedback to improve signal attenuation due to passivation capacitance and a low-leakage floating-gate reset followed by a digital correlated double sampling to robustly remove unwanted trapped charge-induced dc offset. An automatic gain calibration (AGC) is used to perform real-time calibration and guarantee all sensors that have the same gain with a 99% accuracy, and combining all these mechanisms guarantees an average pixel voltage variation of 14.3 mV after gain is applied when measured over multiple dies. The full array is experimentally shown to be capable of real-time ion imaging of pH, with an intrinsic sensitivity of 39.6mV/pH and a scan rate of 9.3 frames/s when running the AGC, with a total power consumption of 10.2 mW.

P‐51: Analysis of Flicker Improvement Result using Polarity MUX

When Polarity MUX is used, a part of the high voltage is lowered. The effectiveness of low power and response time had already been announced in the existing paper. We also found that Polarity MUX has effective of flicker. Here, we analyzed the effective parts to lower flicker ‐ the kickback voltage of MUX switching that affects the pixel voltage.

Feasibility Study of Integrating Source Driver on Array Using Low-Temperature Polycrystalline Silicon Thin-Film Transistors

In this paper, we proposed a new kind of source driver with fully digital driving and a new approach to implement source driver on array (SoA). For the SoA circuit, the digital/analogue converters and buffers are replaced with pulse width modulation circuit and data voltage setting circuit to simplify the source driver. Thus, the signal converting part in the conventional source driver can be omitted and is much more easy to be built with thin-film transistors on the glass. Further, the feasibility of integrating SoA will be studied in the practical way. The layout area and power consumption are found to be the obstacles if we want to use the current thin-film transistor technology to implement SoA. However, the fully digital driving concept can be still applied to develop the configuration of digital interface. We can use the external source driver to produce the digital pulse width signal to set the pixel voltage. This method avoids issue of layout area and power consumption. Hence, the concept of digital interface is much more practical and feasible to reduce the cost and power of data driving instead of SoA.

A New Dot Inversion Data Addressing Technique Using Double Rate Driving Method for High Image Quality and Low-Power TFT-LCDs

This paper proposes a new dot inversion data addressing technique to achieve a high image quality in thin film transistor liquid crystal displays (TFT-LCDs) using a double rate driving method. The proposed data addressing technique optimizes the charging sequence of subpixels to reduce the variation in pixel voltage caused by parasitic capacitance, while maintaining the low-power consumption of the data driver IC. To verify the performance of the proposed technique, three 17-inch full high-definition fringe field switching mode TFT-LCD samples were fabricated and evaluated. The deviation of the green subpixel luminance using a test pattern (R0, G127, B255) is less than two gray levels, and the power consumption of the data driver IC when displaying a mosaic pattern is reduced to 3.6 W at a 13 V supply voltage. In addition, a new pixel structure with a high 59.4% aperture ratio reduces the power consumption of the backlight unit to 9.8 W, which is 16% less than a conventional design.

Noise power spectrum of the fixed pattern noise in digital radiography detectors.

The fixed pattern noise in radiography image detectors is caused by various sources. Multiple readout circuits with gate drivers and charge amplifiers are used to efficiently acquire the pixel voltage signals. However, the multiple circuits are not identical and thus yield nonuniform system gains. Nonuniform sensitivities are also produced from local variations in the charge collection elements. Furthermore, in phosphor-based detectors, the optical scattering at the top surface of the columnar CsI growth, the grain boundaries, and the disorder structure causes spatial sensitivity variations. These nonuniform gains or sensitivities cause fixed pattern noise and degrade the detector performance, even though the noise problem can be partially alleviated by using gain correction techniques. Hence, in order to develop good detectors, comparative analysis of the energy spectrum of the fixed pattern noise is important. In order to observe the energy spectrum of the fixed pattern noise, a normalized noise power spectrum (NNPS) of the fixed pattern noise is considered in this paper. Since the fixed pattern noise is mainly caused by the nonuniform gains, we call the spectrum the gain NNPS. We first asymptotically observe the gain NNPS and then formulate two relationships to calculate the gain NNPS based on a nonuniform-gain model. Since the gain NNPS values are quite low compared to the usual NNPS, measuring such a low NNPS value is difficult. By using the average of the uniform exposure images, a robust measuring method for the gain NNPS is proposed in this paper. By using the proposed measuring method, the gain NNPS curves of several prototypes of general radiography and mammography detectors were measured to analyze their fixed pattern noise properties. We notice that a direct detector, which is based on the a-Se photoconductor, showed lower gain NNPS than the indirect-detector case, which is based on the CsI scintillator. By comparing the gain NNPS curves of the indirect detectors, we could analyze the scintillator properties depending on the techniques for the scintillator surface processing. A robust measuring method for the NNPS of the fixed pattern noise of a radiography detector is proposed in this paper. The method can measure a stable gain NNPS curve, even though the fixed pattern noise level is quite low. From the measured gain NNPS curves, we can compare and analyze the detector properties in terms of producing the fixed pattern noise.

Design and Simulation of the Pixel Circuit for a 6-in Full HD LTPS TFT LCD Based on the New Digital Driving Method

For all of the electronic modules in a liquid crystal display (LCD), the power consumption of data driver is only second to the backlight. Most of the power is used for converting the signal from digital to analog. In this paper, we proposed a new kind of pixel circuit with fully digital driving. As a result, the signal converting part in the conventional data driver can be omitted, and thus the power consumption can be greatly reduced. The proposed pixel circuit contains two thin-film transistors (TFTs) and a resistor in series, forming a discharging path for pixel voltage. There is also another transistor used to preset the pixel voltage. The gray level is controlled by the pulse width of the data source when the pixel is enabled by the scan voltage. The operation of the novel design is verified by simulation in the cases of a full high-definition panel. The proposed pixel circuit with the new driving method is an innovation approach to reduce data driver power consumption.

P‐41: Active Matrix Display with In‐Pixel Digital‐Analogue Conversion Driven by Digital Pulse Width Modulation

AbstractThe paper proposes a new concept to drive the display pixel by modulating the pulse width of data voltage to control the discharge through a resistor of the pixel voltage. Thus, the D/A converters, output buffers, as well as the reference voltages in the conventional data driver can be omitted. Without those circuits, the power and cost of the active matrix display can be further reduced.