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 Photoplethysmography System Optimised for Pervasive Cardiac Monitoring

Photoplethysmography is a non-invasive sensing technique which infers instantaneous cardiac function from an optical measurement of blood vessels. This thesis presents a photoplethysmography based sensor system that has been developed speci fically for the requirements of a pervasive healthcare monitoring system. Continuous monitoring of patients requires both the size and power consumption of the chosen sensor solution to be minimised to ensure the patients will be willing to use the device. Pervasive sensing also requires that the device be scalable for manufacturing in high volume at a build cost that healthcare providers are willing to accept. System level choice of both electronic circuits and signal processing techniques are based on their sensitivity to cardiac biosignals, robustness against noise inducing artefacts and simplicity of implementation. Numerical analysis is used to justify the implementation of a technique in hardware. Circuit prototyping and experimental data collection is used to validate a technique's application. The entire signal chain operates in the discrete-time domain which allows all of the signal processing to be implemented in firmware on an embedded processor which minimised the number of discrete components while optimising the trade-off between power and bandwidth in the analogue front-end. Synchronisation of the optical illumination and detection modules enables high dynamic range rejection of both AC and DC independent light sources without compromising the biosignal. Signal delineation is used to reduce the required communication bandwidth as it preserves both amplitude and temporal resolution of the non-stationary photoplethysmography signals allowing more complicated analytical techniques to be performed at the other end of communication channel. The complete sensing system is implemented on a single PCB using only commercial-off -the-shelf components and consumes less than 7.5mW of power. The sensor platform is validated by the successful capture of physiological data in a harsh optical sensing environment

A Photoplethysmography System Optimised for Pervasive Cardiac Monitoring

Photoplethysmography is a non-invasive sensing technique which infers instantaneous cardiac function from an optical measurement of blood vessels. This thesis presents a photoplethysmography based sensor system that has been developed speci fically for the requirements of a pervasive healthcare monitoring system. Continuous monitoring of patients requires both the size and power consumption of the chosen sensor solution to be minimised to ensure the patients will be willing to use the device. Pervasive sensing also requires that the device be scalable for manufacturing in high volume at a build cost that healthcare providers are willing to accept. System level choice of both electronic circuits and signal processing techniques are based on their sensitivity to cardiac biosignals, robustness against noise inducing artefacts and simplicity of implementation. Numerical analysis is used to justify the implementation of a technique in hardware. Circuit prototyping and experimental data collection is used to validate a technique's application. The entire signal chain operates in the discrete-time domain which allows all of the signal processing to be implemented in firmware on an embedded processor which minimised the number of discrete components while optimising the trade-off between power and bandwidth in the analogue front-end. Synchronisation of the optical illumination and detection modules enables high dynamic range rejection of both AC and DC independent light sources without compromising the biosignal. Signal delineation is used to reduce the required communication bandwidth as it preserves both amplitude and temporal resolution of the non-stationary photoplethysmography signals allowing more complicated analytical techniques to be performed at the other end of communication channel. The complete sensing system is implemented on a single PCB using only commercial-off -the-shelf components and consumes less than 7.5mW of power. The sensor platform is validated by the successful capture of physiological data in a harsh optical sensing environment

Space station data system analysis/architecture study. Task 2: Options development DR-5. Volume 1: Technology options

The second task in the Space Station Data System (SSDS) Analysis/Architecture Study is the development of an information base that will support the conduct of trade studies and provide sufficient data to make key design/programmatic decisions. This volume identifies the preferred options in the technology category and characterizes these options with respect to performance attributes, constraints, cost, and risk. The technology category includes advanced materials, processes, and techniques that can be used to enhance the implementation of SSDS design structures. The specific areas discussed are mass storage, including space and round on-line storage and off-line storage; man/machine interface; data processing hardware, including flight computers and advanced/fault tolerant computer architectures; and software, including data compression algorithms, on-board high level languages, and software tools. Also discussed are artificial intelligence applications and hard-wire communications

A High Rate Testbeam Data Acquisition System and Characterization of High Voltage Monolithic Active Pixel Sensors

New experiments, designed to test the Standard Model of particle physics with unprecedented precision and to search for physics beyond, push detector technologies to their limits. The Mu3e experiment searches for the charged lepton flavor violating decay μ+ → e+e−e+ with a branching ratio sensitivity of better than 1 ·10−16. This decay is suppressed in the StandardModel to unobservable levels but can be sizable in models beyond the Standard Model. The Mu3e detector consists of a thin pixel spectrometer combined with scintillating detectors to measure the vertex, momentum and time of the decay particles. Requirements on rate and material budget cannot be fulfilled by classical pixel sensors and demand the development of a novel pixel technology: high-voltage monolithic active pixel sensors (HV-MAPS). Two important steps towards a final pixel detector are discussed within the scope of this thesis: the characterization of two HV-MAPS prototypes from the MUPIX family and the development of a tracking telescope based on HV-MAPS with online monitoring, tracking and efficiency calculation for particle rates above 10 MHz. Using the telescope it is shown that the transition from the small-scale MUPIX7 to the full-scale MUPIX8 has been successful. Sensor characterization studies of the MUPIX8 show efficiencies above 99% at noise rates below 0.4 Hz/pixel over a large threshold range as well as a time resolution of 6.5 ns after time-walk corrections, thus fulfilling allMu3e sensor requirements. Additionally, the radiation tolerance of the MUPIX7 has been demonstrated up to a fluence of 1.5 ·10+15 24 GeV p/cm2

Smart vision in system-on-chip applications

In the last decade the ability to design and manufacture integrated circuits with higher transistor densities has led to the integration of complete systems on a single silicon die. These are commonly referred to as System-on-Chip (SoC). As SoCs processes can incorporate multiple technologies it is now feasible to produce single chip camera systems with embedded image processing, known as Imager-on-Chips (IoC). The development of IoCs is complicated due to the mixture of digital and analog components and the high cost of prototyping these designs using silicon processes. There are currently no re-usable prototyping platforms that specifically address the needs of IoC development. This thesis details a new prototyping platform specifically for use in the development of low-cost mass-market IoC applications. FPGA technology was utilised to implement a frame-based processing architecture suitable for supporting a range of real-time imaging and machine vision applications. To demonstrate the effectiveness of the prototyping platform, an example object counting and highlighting application was developed and functionally verified in real-time. A high-level IoC cost model was formulated to calculate the cost of manufacturing prototyped applications as a single IoC. This highlighted the requirement for careful analysis of optical issues, embedded imager array size and the silicon process used to ensure the desired IoC unit cost was achieved. A modified version of the FPGA architecture, which would result in improving the DSP performance, is also proposed

NASA Tech Briefs, May 1996

Topics include: Video and Imaging;Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Report

State of the art survey of technologies applicable to NASA's aeronautics, avionics and controls program

The state of the art survey (SOAS) covers six technology areas including flightpath management, aircraft control system, crew station technology, interface & integration technology, military technology, and fundamental technology. The SOAS included contributions from over 70 individuals in industry, government, and the universities

Exhaled breath condensate based breath analyser

Exhaled breath condensate (EBC) based breath analysis has gained significant interest in pulmonary disease diagnostics over the past few years due to the non-invasiveness and simplicity of the technique. Most approaches to date have separated EBC collection from the subsequent lab-based analysis, more notably, integrated EBC collector and analyser do not exist. Under current suggested protocol EBC samples for hydrogen peroxide analysis needs freezing at -70 C immediately after collection but still exhibit instabilities in concentration. To address those difficulties and to provide easy-to-use devices for patients, we have proposed a portable integrated EBC analyser, which gives measurement results within 3 minutes. The device incorporates Peltier cooling for sample collection; electronics control system and a disposable chemically modified amperometric sensor. Cooling system and device architecture were designed based on thermofluidic analysis of Falkner-Skan solution. Theoretical modelling and experimental evidence suggest that previously reported large variations between analyte concentrations arise from poor control of the condensation process. Fundamental studies suggest higher condensation temperature favours more concentrated analyte collection, relieving the burden on electrochemical sensor limit of detection (LOD). Low hydrogen peroxide in EBC presents another challenge. We have developed a modified Prussian blue (PB) sensor, by blending PB in conducting polymer matrix to increase PB density on electrode as well as cross linking matrix to improve the mechanical properties and enhance processability. Full mechanistic investigation using rotation disk electrode and chronoamperometry experiments reveal the kinetics of the sensor and informed subsequent development. The sensor has been demonstrated to measure hydrogen peroxide in EBC.Open Acces