89 research outputs found
Low-Power and High-Performance Drivers for OLEDoS Microdisplays
The rapid growth of the microdisplay market, driven by the demand for smartwatches, head-mounted displays in Virtual Reality (VR) and Augmented Reality (AR), and other portable devices, has presented a need to enhance their energy efficiency. This thesis focuses on reducing the power and energy consumption of microdisplays while maintaining display luminance, and image quality; and enhancing key features such as resolution, refresh rate, and color depth.
First, a novel driving method and pixel circuit are proposed that reduces the number of subframes in a digitally-driven display. The dual-driver method offers flexibility in different design modes, allowing for the enhancement of various display characteristics. In the low-power mode, the operating frequency is reduced, resulting in decreased dynamic power consumption by the drivers. Experimental results on a proof-of-concept array fabricated using TSMC 65 nm technology demonstrate a significant 39% reduction in power consumption compared to a conventional array. Furthermore, designing the display in other modes yields remarkable improvements, with up to 8.5 times enhancement in refresh rate or resolution. In addition, the high color depth mode presents an opportunity to increase color depth from 8 bits to 14 bits, enhancing the visual experience.
Additionally, this thesis investigates power reduction techniques specific to row drivers in microdisplays. Circuit techniques are proposed to recycle energy in the row driver, thereby reducing dynamic power consumption. Measurement results on proof-of-concept arrays implemented in TSMC 65 nm technology reveal substantial reductions of up to 30% in the power consumption of the row driver using different energy recycling techniques. Applying these techniques led to a significant reduction in the dynamic power consumption of the row driver. For instance, employing the direct energy restoration technique resulted in a remarkable decrease of over 45% in the dynamic power consumption of the row driver.
Finally, a digital data driver with a data energy recycling feature is presented to further reduce the dynamic power consumption of microdisplays. Measurement results obtained from a proof-of-concept array fabricated using TSMC 65 nm technology demonstrate an average power consumption reduction of 16% in the display’s data driver when subjected to randomly generated test images.
This thesis addresses the pressing need for energy-efficient microdisplays, offering innovative driving methods, pixel circuit design, and dynamic power reduction techniques. The proposed solutions provide significant power savings while preserving display quality and enabling enhancements in resolution, refresh rate, and color depth, contributing to extended battery life and improved user experience in portable electronic systems
Design and characterisation of a ferroelectric liquid crystal over silicon spatial light modulator
Many optical processing systems rely critically on the availability of high
performance, electrically-addressed spatial light modulators. Ferroelectric liquid
crystal over silicon is an attractive spatial light modulator technology because it
combines two well matched technologies. Ferroelectric liquid crystal modulating
materials exhibit fast switching times with low operating voltages, while very
large scale silicon integrated circuits offer high-frequency, low power operation,
and versatile functionality.
This thesis describes the design and characterisation of the SBS256 - a general
purpose 256 x 256 pixel ferroelectric liquid crystal over silicon spatial light modulator
that incorporates a static-RAM latch and an exclusive-OR gate at each
pixel. The static-RAM latch provides robust data storage under high read-beam
intensities, while the exclusive-OR gate permits the liquid crystal layer to be fully
and efficiently charge balanced.
The SBS256 spatial light modulator operates in a binary mode. However,
many applications, including helmet-mounted displays and optoelectronic implementations
of artificial neural networks, require devices with some level of
grey-scale capability. The 2 kHz frame rate of the device, permits temporal multiplexing
to be used as a means of generating discrete grey-scale in real-time.
A second integrated circuit design is also presented. This prototype neuraldetector
backplane consists of a 4 x 4 array of optical-in, electronic-out processing
units. These can sample the temporally multiplexed grey-scale generated by the
SBS256. The neurons implement the post-synaptic summing and thresholding
function, and can respond to both positive and negative activations - a requirement
of many artificial neural network models
Active Matrix Flat Panel Bio-Medical X-ray Imagers
This work investigates the design, system integration, optimization, and evaluation of amorphous silicon (a-Si:H) active matrix flat panel imagers (AMFPI) for bio-medical applications. Here, two hybrid active pixel sensor (H-APS) designs are introduced that improve the dynamic range while maintaining the desirable attributes of high speed and low noise readout. Also presented is a systematic approach for noise analysis of thin film transistors (TFT) and pixel circuits in which circuit analysis techniques and TFT noise models are combined to evaluate circuit noise performance. We also explore different options of system integration and present measurement results of a high fill-factor (HFF) array with segmented photodiode
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Flat Panel Displays in an Automotive Environment
A study was made of the field of flat panel displays, and their potential application in an automotive environment. Using contemporary display technology, semiconductors and software, a model was developed to fit an existing automotive instrumentation application. The resulting model was critically assessed in respect to the demands of such an application in respect to existing instrumentation methods. The viability and suitability of implementing such a design are discussed as well as its ability to be intrinsically portable and adaptable
Development of an acoustic measurement system of the Modulus of Elasticity in trees, logs and boards
The objective of this Bachelor’s Thesis is to develop a portable electronic device capable of quantifying
the stiffness of the wood of standing trees, logs and boards using non-destructive testing (NDT) by means
of acoustic wave analysis. As an indicator of stiffness, the Modulus of Elasticity (MOE) is used, a standard
figure in the industry. This way, wood from forestry can be characterized and classified for different purposes.
This Thesis is part of LIFE Wood For Future, a project of the University of Granada (UGR) financed by
the European Union’s LIFE programme. LIFE Wood For Future aims to recover the cultivation of poplar
(populus sp.) in the Vega de Granada, by proving the quality of its wood through innovative structural
bioproducts. Recovering the poplar groves of Granada would have great benefits for the Metropolitan Area:
creation of local and sustainable jobs, improvement of biodiversity, and increase in the absorption of carbon
dioxide in the long term, helping to reduce the endemic air pollution of Granada. This Final Degree Project
has been developed in collaboration with the ADIME research group of the Higher Technical School of
Building Engineering (ETSIE) and the aerospace electronics group GranaSat of the UGR.
The goal of the developed device, named Tree Inspection Kit (or TIK), is to be an innovative, portable
and easy-to-use tool for non-destructive diagnosis and classification of wood by measuring its MOE. TIK
is equipped with the necessary electronics to quantify the Time of Flight (ToF) of an acoustic wave that
propagates inside a piece of wood. In order to do this, two piezoelectric probes are used, nailed in the wood
and separated a given distance longitudinally. The MOE can be derived from the propagation speed of the
longitudinal acoustic wave if the density of the is known. For this reason, this device has the possibility of
connecting a load cell for weighing logs or boards to estimate their density. It also has an expansion port
reserved for future functionality.
A methodology based on the Engineering Design Process (EDP) has been followed. The scope of this
project embraces all aspects of the development of an electronic product from start to finish:
conceptualization, specification of requirements, design, manufacture and verification. A project of this
reach requires planning, advanced knowledge of signal analysis, electronics, design and manufacture of
Printed Circuit Boards (PCB) and product design, as well as the development of a firmware for the
embedded system, based on a RTOS. Prior to the design of the electronics, a Reverse Engineering process
of some similar products of the competition is performed; as well as an exhaustive analysis of the signals
coming from the piezoelectric sensors that are going to be used, and the frequency response
characterization of the piezoelectric probes themselves.
This project has as its ultimate goal the demonstration of the multidisciplinary knowledge of engineering,
and the capacity of analysis, design and manufacturing by the author; his skill and professionalism in CAD
and EDA software required for these tasks, as well as in the documentation of the entire process.El presente Trabajo de Fin de Grado tiene como objetivo el desarrollo de un dispositivo electrónico
portátil capaz de cuantificar la rigidez de la madera de árboles en pie, trozas y tablas usando ensayos no
destructivos (Non-Destructive Testing, NDT) por medio del análisis de ondas acústicas. Como indicador de
la rigidez se usa el Módulo de Elasticidad (MOE), una figura estándar en la industria.
Este TFG forma parte de LIFE Wood For Future, un proyecto de la Universidad de Granada (UGR)
financiado por el programa LIFE de la Unión Europea. LIFEWood For Future tiene como objetivo recuperar
el cultivo del chopo (populus sp.) en la Vega de Granada demostrando la viabilidad de su madera a través
de bioproductos estructurales innovadores. Recuperar las choperas de Granada tendría grandes beneficios
para la zona del Área Metropolitana: creación de puestos de trabajo locales y sostenibles, mejora de la
biodiversidad, e incremento de la tasa de absorción de dióxido de carbono a largo plazo, contribuyendo a
reducir la contaminación endémica del aire en Granada. Este Trabajo de Fin de Grado se ha desarrollado
con la colaboración del grupo de investigación ADIME de la Escuela Técnica Superior de Ingeniería de
Edificación (ETSIE) y el grupo de electrónica aeroespacial GranaSat de la UGR.
El objetivo del dispositivo, denominado Tree Inspection Kit (TIK), es ser una herramienta innovadora,
portátil y fácil de usar para el diagnóstico y clasificación no destructiva de la madera por medio de su MOE.
TIK está dotado de la electrónica necesaria para medir el tiempo de tránsito (ToF) de una onda acústica que
se propaga en el interior de una pieza de madera. Para ello, se utilizan dos sondas piezoeléctricas clavadas
en la madera y separadas longitudinalmente una distancia conocida. De la velocidad de propagación de la
onda longitudinal se puede derivar el MOE, previo conocimiento de la densidad del material. Por ello, este
dispositivo cuenta con la posibilidad de conectarle una célula de carga y pesar trozas o tablas para estimar
su densidad. También tiene un puerto de expansión reservado para funcionalidad futura.
Se ha seguido una metodología basada en el Proceso de Diseño de Ingeniería (Engineering Design
Process, EDP), abarcando todos los aspectos del desarrollo de un producto electrónico de principio a fin:
conceptualización, especificación de requisitos, diseño, fabricación y verificación. Un proyecto de este
alcance requiere de planificación, conocimientos avanzados de análisis de señales, de electrónica, de diseño y
fabricación de Placas de Circuito Impreso (PCB) y de diseño de producto, así como el desarrollo de un
firmware para el sistema empotrado, basado en un RTOS. Previo al diseño de la electrónica, se realiza un
proceso de Ingeniería Inversa (Reverse Engineering) de algunos productos similares de la competencia; al
igual que un exhaustivo análisis de las señales provenientes de los sensores piezoeléctricos que van a
utilizarse y la caracterización en frecuencia de las propias sondas piezoeléctricas.
Este proyecto tiene como fin último la demostración de los conocimientos multidisciplinares propios de la
ingeniería y la capacidad de análisis, diseño y fabricación por parte del autor; su habilidad y profesionalidad
en el software CAD y EDA requerido para estas tareas, así como en la documentación de todo el proceso.Unión Europe
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Flat Panel Displays in Perspective
This report addresses two issues. First, is the lack of a high-volume domestic FPD industry a cause for national concern? Why might having such an industry be important for the good of the nation? Second, if the government wishes to foster such an industry, what policies might be most effective
Pixel design and characterization of high-performance tandem OLED microdisplays
Organic Light-Emitting Diode (OLED) microdisplays - miniature Electronic Displays comprising a
sandwich of organic light emitting diode over a substrate containing CMOS circuits designed to function
as an active matrix backplane – were first reported in the 1990s and, since then, have advanced to the
mainstream. The smaller dimensions and higher performance of CMOS circuit elements compared to
that of equivalent thin film transistors implemented in technologies for large OLED display panels offer
a distinct advantage for ultra-miniature display screens. Conventional OLED has suffered from lifetime
degradation at high brightness and high current density. Recently, tandem-structure OLED devices have
been developed using charge generation layers to implement two or more OLED units in a single stack.
They can achieve higher brightness at a given current density. The combination of emissive-nature, fast
response, medium to high luminance, low power consumption and appropriate lifetime makes OLED a
favoured candidate for near-to-eye systems. However, it is also challenging to evaluate the pixel level
optical response of OLED microdisplays as the pixel pitch is extremely small and relative low light
output per pixel. Advanced CMOS Single Photon Avalanche Diode (SPAD) technology is progressing
rapidly and is being deployed in a wide range of applications. It is also suggested as a replacement for
photomultiplier tube (PMT) for photonic experiments that require high sensitivity. CMOS SPAD is a
potential tool for better and cheaper display optical characterizations.
In order to incorporate the novel tandem structure OLED within the computer aided design (CAD) flow
of microdisplays, we have developed an equivalent circuit model that accurately describes the tandem
OLED electrical characteristics. Specifically, new analogue pulse width modulation (PWM) pixel
circuit designs have been implemented and fabricated in small arrays for test and characterization
purposes. We report on the design and characterization of these novel pixel drive circuits for OLED
microdisplays. Our drive circuits are designed to allow a state-of-the-art sub-pixel pitch of around 5 μm
and implemented in 130 nm CMOS. A performance comparison with a previous published analogue
PWM pixel is reported. Moreover, we have employed CMOS SPAD sensors to perform detailed optical
measurements on the OLED microdisplay pixels at very high sampling rate (50 kHz, 10 μs exposure),
very low light level (2×10-4 cd/m2) and over a very wide dynamic range (83 dB) of luminance. This
offers a clear demonstration of the potential of the CMOS SPAD technology to reveal hitherto obscure
details of the optical characteristics of individual and groups of OLED pixels and thereby in display
metrology in general.
In summary, there are three key contributions to knowledge reported in this thesis. The first is a new
equivalent circuit model specifically for tandem structure OLED. The model is verified to provide
accurately illustrate the electrical response of the tandem OLED with different materials. The second is
the novel analogue PWM pixel achieve a 5μm sub-pixel pitch with 2.4 % pixel-to-pixel variation. The
third is the new application and successful characterization experiment of OLED microdisplay pixels
with SPAD sensors. It revealed the OLED pixel overshoot behaviour with a QIS SPAD sensor
A triage approach to streamline environmental footprinting : a case study for liquid crystal displays
Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 64-69).Quantitative environmental performance evaluation methods are desired given the growing certification and labeling landscape for consumer goods. Challenges associated with existing methods, such as life cycle assessment (LCA), may be prohibitive for complex goods such as information technology (IT). Conventional LCA is resource-intensive and lacks harmonized guidance for incorporating uncertainty. Current methods to streamline LCA may amplify uncertainty, undermining robustness. Despite high uncertainty, effective and efficient streamlining approaches may be possible. A methodology is proposed to identify high-impact activities within the life cycle of a specific product class for a streamlined assessment with a high degree of inherent uncertainty. First, a screening assessment is performed using Monte Carlo simulations, applying existing activity (materials and processes), impact, and uncertainty data, to identify elements with the most leverage to reduce overall environmental impact uncertainty. This data triage is informed by sensitivity analysis parameters produced by the simulations. Targeted data collection is carried out for key activities until overall uncertainty is reduced to the point where a product classes' impact probability distribution is distinct from others within a specified error rate. In this thesis, we find that triage and prioritization are possible despite high uncertainty. The methodology was applied to the case study of liquid crystal display (LCD) classes, producing a clear hierarchy of data importance to reduce uncertainty of the overall impact result. Specific data collection was only required for a subset of processes and activities (22 out of about 50) to enable discrimination of LCDs with a low error rate (9%). Most of these priority activities relate to manufacturing and use phases. The number of priority activities targeted may be balanced with the level to which they are able to be specified. It was found that ostensible product attributes alone are insufficient to discriminate with low error, even at high levels of specificity. This quantitative streamlining method is ideal for complex products for which there is great uncertainty in data collection and modeling. This application of this method may inform early product design decisions and enable harmonization of standardization efforts.by Melissa Lee Zgola.S.M.in Technology and Polic
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