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(1 - 6 of 6)
- Title
- A FPGA-BASED ARCHITECTURE FOR LED BACKLIGHT DRIVING.
- Creator
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Zheng, Zhaoshi, Zhou, Huiyang, University of Central Florida
- Abstract / Description
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In recent years, Light-emitting Diodes (LEDs) have become a promising candidate for backlighting Liquid Crystal Displays (LCDs). Compared with traditional Cold Cathode Fluorescent Lamps (CCFLs) technology, LEDs offer not only better visual quality, but also improved power efficiency. However, to fully utilized LEDs' capability requires dynamic independent control of individual LEDs, which remains as a challenging topic. A FPGA-based hardware system for LED backlight control is proposed in...
Show moreIn recent years, Light-emitting Diodes (LEDs) have become a promising candidate for backlighting Liquid Crystal Displays (LCDs). Compared with traditional Cold Cathode Fluorescent Lamps (CCFLs) technology, LEDs offer not only better visual quality, but also improved power efficiency. However, to fully utilized LEDs' capability requires dynamic independent control of individual LEDs, which remains as a challenging topic. A FPGA-based hardware system for LED backlight control is proposed in this work. We successfully achieve dynamic adjustment of any individual LED' intensity in each of the three color channels (Red, Green and Blue), in response to a real time incoming video stream. In computing LED intensity, four video content processing algorithms have been implemented and tested, including averaging, histogram equalization, LED zone pattern change detection and non-linear mapping. We also construct two versions of the system. The first employs an embedded processor which performs the above-mentioned algorithms on pre-processed video data; the second embodies the same functionality as the first on fixed hardware logic for better performance and power efficiency. The system servers as the backbone of a consolidated display, which yields better visual quality than common commercial displays, we build in collaboration with a group of researchers from CREOL at UCF.
Show less - Date Issued
- 2010
- Identifier
- CFE0003351, ucf:48451
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003351
- Title
- Joint Optimization of Illumination and Communication for a Multi-Element VLC Architecture.
- Creator
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Ibne Mushfique, Sifat, Yuksel, Murat, Pourmohammadi Fallah, Yaser, Turgut, Damla, University of Central Florida
- Abstract / Description
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Because of the ever increasing demand wireless data in the modern era, the Radio Frequency (RF) spectrum is becoming more congested. The remaining RF spectrum is being shrunk at a very heavy rate, and spectral management is becoming more difficult. Mobile data is estimated to grow more than 10 times between 2013 and 2019, and due to this explosion in data usage, mobile operators are having serious concerns focusing on public Wireless Fidelity (Wi-Fi) and other alternative technologies....
Show moreBecause of the ever increasing demand wireless data in the modern era, the Radio Frequency (RF) spectrum is becoming more congested. The remaining RF spectrum is being shrunk at a very heavy rate, and spectral management is becoming more difficult. Mobile data is estimated to grow more than 10 times between 2013 and 2019, and due to this explosion in data usage, mobile operators are having serious concerns focusing on public Wireless Fidelity (Wi-Fi) and other alternative technologies. Visible Light Communication (VLC) is a recent promising technology complementary to RF spectrum which operates at the visible light spectrum band (roughly 400 THz to 780 THz) and it has 10,000 times bigger size than radio waves (roughly 3 kHz to 300 GHz). Due to this tremendous potential, VLC has captured a lot of interest recently as there is already an extensive deployment of energy efficient Light Emitting Diodes (LEDs). The advancements in LED technology with fast nanosecond switching times is also very encouraging. In this work, we present hybrid RF/VLC architecture which is capable of providing simultaneous lighting and communication coverage in an indoor setting. The architecture consists of a multi-element hemispherical bulb design, where it is possible to transmit multiple data streams from the multi-element hemispherical bulb using LED modules. We present the detailed components of the architecture and make simulations considering various VLC transmitter configurations. Also, we devise an approach for an efficient bulb design mechanism to maintain both illumination and communication at a satisfactory rate, and analyze it in the case of two users in a room. The approach involves formulating an optimization problem and tackling the problem using a simple partitioning algorithm. The results indicate that good link quality and high spatial reuse can be maintained in a typical indoor communication setting.
Show less - Date Issued
- 2018
- Identifier
- CFE0007016, ucf:52025
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007016
- Title
- Non-Dispersive Infrared (NDIR) Gas Sensor Utilizing Light-Emitting-Diodes Suitable for Applications Demanding Low-Power and Lightweight Instruments.
- Creator
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Thurmond, Kyle, Vasu Sumathi, Subith, Kassab, Alain, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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Gas sensors that are low-power, light-weight, and rugged, while also remaining low-cost, have considerable appeal to areas from automotive to space flight. There are increasing demands for higher efficient vehicles with lower emissions in order meet regulations that are meant to mitigate or lessen the effects of climate change. An affordable, fast response sensor that can measure transient carbon monoxide (CO) and carbon dioxide (CO2) has broad application which can lead to more efficient,...
Show moreGas sensors that are low-power, light-weight, and rugged, while also remaining low-cost, have considerable appeal to areas from automotive to space flight. There are increasing demands for higher efficient vehicles with lower emissions in order meet regulations that are meant to mitigate or lessen the effects of climate change. An affordable, fast response sensor that can measure transient carbon monoxide (CO) and carbon dioxide (CO2) has broad application which can lead to more efficient, fuel flexible engines and regulations of harmful emissions. With compact, economical, low-power sensors that are able to continually monitor gases that are characteristic of burning materials, a distributed sensor array could be implemented on space vehicles that would allow early detection of fires, gas leaks, or other critical events. With careful selection of targeted gases, it may be possible to identify the material that is burning or smoldering, better informing the crew so that they may respond and prioritize high emergency events. Further applications may include fuel/ hazardous gas leak detection on space vehicles and atmospheric constituent sensor for portable life support systems (PLSS) used by astronauts in extra vehicular activity (EVA). Non-dispersive infrared (NDIR) sensors are attractive due to their simplicity and low-cost; and by using light-emitting-diodes (LEDs) in this approach, power efficient, light-weight, and stable gas sensors can be developed to meet these needs.This thesis discusses a sensor that was developed for simultaneous, time resolved measurements of carbon monoxide (CO) and carbon dioxide (CO2). This sensor utilizes low-cost and compact light emitting diodes (LEDs) that emit in the 3-5?m wavelength range. Light emission of LEDs is spectrally broader and more spatially divergent compared to that of lasers, which presented many design challenges. Optical design studies addressed some of the non-ideal characteristics of the LED emissions. Measurements of CO and CO2 were conducted using their fundamental absorption bands centered at 4.7?m and 4.3?m, respectively, while a 3.6?m reference LED was used to account for scattering losses (e.g., due to soot, window deposits, etc.) common to the three measurement LEDs. Instrument validation and calibration was performed using a laboratory flow cell and bottled-gas mixtures. The sensor was able to detect CO2 and CO concentration changes as small as 30 ppm and 400 ppm, respectively. Because of the many control and monitor species with infra-red absorption features, which can be measured using the strategy described, this work demonstrates proof of concept for a wider range of fast (250Hz) and low cost sensors for gas measurement and process monitoring.
Show less - Date Issued
- 2016
- Identifier
- CFE0006190, ucf:51091
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006190
- Title
- Mid-Infrared Absorption Spectrometer for Multi-Species Detection Using LEDs for Space Applications: Development and Flight Testing.
- Creator
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Villar, Michael, Vasu Sumathi, Subith, Chow, Louis, Partridge, William, University of Central Florida
- Abstract / Description
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As commercial space travel expands, the need for specialized instrumentation to ensure the safety of crew and cargo becomes increasingly necessary. Both the Federal Aviation Administration (FAA) and pioneers in the space tourism industry have expressed an interest in a robust, low cost, and low power consumption sensor to measure atmospheric composition aboard spacecraft. To achieve this goal a time-resolved NDIR absorption sensor that measures transient levels of gaseous carbon dioxide (CO2)...
Show moreAs commercial space travel expands, the need for specialized instrumentation to ensure the safety of crew and cargo becomes increasingly necessary. Both the Federal Aviation Administration (FAA) and pioneers in the space tourism industry have expressed an interest in a robust, low cost, and low power consumption sensor to measure atmospheric composition aboard spacecraft. To achieve this goal a time-resolved NDIR absorption sensor that measures transient levels of gaseous carbon dioxide (CO2) and carbon monoxide (CO) was developed. The developed sensor has a wide range of applications applicable to the growing needs of industry, from monitoring CO and CO2 levels for crew cabin safety to early detection of gas leaks, fires, or other atmospheric altering events. A proof of concept, lab-bench dependent sensor has been previously developed to begin to target the needs of this industry. This thesis discusses the expansion and evolution from this previous lab-bench dependent design into a portable, autonomous, and remote sensor that is able to withstand the harsh environmental conditions required for its intended operation in near space. The sensor incorporates compact high-efficiency LEDs that transmit in the 3-5?m wavelength range. These LEDs are further centered at 4.2?m and 4.7?m by the use of narrow band-pass filters to measure the spectral absorbance features of CO2 and CO respectively. Active and passive thermal management of all components is achieved via thermal electric coolers (TEC) and thermal sinks to enable sensor temperature control in applicable low convection environments. To accomplish the needs for a stand-alone sensor, remote and autonomous operation is achieved via the inclusion of a real-time embedded controller with configurable FPGA/IO modules that autonomously handle thermal management, LED operation, and signal data acquisition/storage. Initial instrument validation was completed by utilizing a thermal vacuum chamber with a testable temperature and pressure range from standard temperature and pressure (STP) down to -22(&)deg;F and 8mbar. Variable measurements of CO/CO2/N2 gas mixtures were supplied via mass flow controllers to the sensor's gas cell in order to determine various key metrics of sensor operation. The culmination of the sensor's operational validation was via its flight aboard a NASA funded Louisiana State University (LSU) high-altitude balloon. This flight reached an altitude of 123,546ft with ambient temperatures and static pressures ranging from 910mbar and 53(&)deg;F at ground level to .68mbar and -54(&)deg;F at float altitude. A total mission time of 18h:09m:30s was reached with a total float time of 15h:08m:54s. Successful sensor operation was achieved throughout the entire mission which demonstrates the applicability, adaptability, and relevance of the technologies discussed here for space applications.
Show less - Date Issued
- 2017
- Identifier
- CFE0006671, ucf:51238
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006671
- Title
- monolithically Integrated Broadly Tunable Light Emitters based on Selectively Intermixed Quantum Wells.
- Creator
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Zakariya, Abdullah, Likamwa, Patrick, Li, Guifang, Wahid, Parveen, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
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A monolithically integrated broadly tunable MQW laser that utilizes a combined impurity-free vacancy disordering (IFVD) of quantum wells and optical beam steering techniques is proposed and investigated experimentally. The device consists of a beam-steering section and an optical amplifier section fabricated on a GaAs/AlGaAs quantum well (QW) p-i-n heterostructure. The beam steering section forms a reconfigurable optical waveguide that can be moved laterally by applying separately controlled...
Show moreA monolithically integrated broadly tunable MQW laser that utilizes a combined impurity-free vacancy disordering (IFVD) of quantum wells and optical beam steering techniques is proposed and investigated experimentally. The device consists of a beam-steering section and an optical amplifier section fabricated on a GaAs/AlGaAs quantum well (QW) p-i-n heterostructure. The beam steering section forms a reconfigurable optical waveguide that can be moved laterally by applying separately controlled electrical currents to two parallel contact stripes. The active core of the gain section is divided in into selectively intermixed regions. The selective intermixing of the QW in the gain section results in neighboring regions with different optical bandgaps. The wavelength tuning is accomplished by steering the amplified optical beam through the selected region where it experiences a peak in the gain spectrum determined by the degree of intermixing of the QW. The laser wavelength tunes to the peak in the gain spectrum of that region. The IFVD technique relies on a silica (SiO2) capped rapid thermal annealing and it has been found that the degree of intermixing of the QW with the barrier material is dependent on the thickness of the SiO2 film. The QW sample is first encapsulated with a 400nm thick SiO2 film grown by plasma enhanced chemical vapor deposition (PECVD). In the gain section, the SiO2 film is selectively etched using multiple photolithographic and reactive ion etching steps whereas the SiO2 film is left intact in all the remaining areas including the beam-steering section. The selective area quantum well intermixing is then induced by a single rapid thermal annealing step at 975(&)deg;C for a 20s duration to realize a structure with quantum well that has different bandgaps in the key regions. Optical characterizations of the intermixed regions have shown a blue shift of peak of the electroluminescence emission of 5nm, 16nm and 33nm for the uncapped, 100nm and 200nm respectively when compared to the as grown sample. The integrated laser exhibited a wavelength tuning range of 17nm (799nm to 816nm). Based on the same principle of QW selective intermixing, we have also designed and fabricated a monolithically integrated multi-wavelength light emitting diode (LED). The LED emits multiple wavelength optical beams from one compact easy to fabricate QW structure. Each wavelength has an independent optical power control, allowing the LED to emit one or more wavelengths at once. The material for the LED is the same AlGaAs/GaAs QW p-i-n heterostructure described above. The device is divided into selectively intermixed regions on a single QW structure using IFVD technique to create localized intermixed regions. Two different designs have been implemented to realize either an LED with multiple output beams of different wavelengths or an LED with a single output beam that has dual wavelength operation capabilities. Experimental results of the multiple output beams LED have demonstrated electrically controlled optical emission of 800nm, 789nm and 772nm. The single output LED has experimentally been shown to produce wavelength emission of 800nm and/or 772nm depending on electrical activation of the two aligned intermixed regions.
Show less - Date Issued
- 2013
- Identifier
- CFE0005284, ucf:50560
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005284
- Title
- DESIGN, FABRICATION, AND TESTING OF HIGH-TRANSPARENCY DEEP ULTRA-VIOLETCONTACTS USING SURFACE PLASMON COUPLING IN SUBWAVELENGTH ALUMINUM MESHES.
- Creator
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Mazuir, Clarisse, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
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The present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms)...
Show moreThe present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms) transmit less than 50% and 30% respectively at 300 nm. Here we investigate the use of surface plasmons (SPs) to design transparent p-contacts for AlGaN devices in the deep UV region of the spectrum. The appeal of using surface plasmon coupling arose from the local electromagnetic field enhancement near the metal surface as well as the increase in interaction time between the field and semiconductor if placed on top of a semiconductor. An in/out-coupling mechanism is achieved by using a grating consisting of two perpendicularly oriented sets of parallel aluminum lines with periods as low as 250 nm. The incident light is first coupled into SPs at the air/aluminum interface which then re-radiate at the aluminum/AlGaN interface and the photons energy is transferred to SP polaritons (SPPs) and back to photons. High transmission can be achieved not only at normal incidence but for a wider range of incident angles. A finite difference time domain (FDTD) package from R-Soft was used to simulate and design such aluminum gratings with transparency as high as 100% with tunable peak wavelength, bandwidth and angular acceptance. A rigorous coupled wave analysis (RCWA) was developed in Matlab to validate the FDTD results. The high UV transparency meshes were then fabricated using an e-beam assisted lithography lift-off process. Their electrical and optical properties were investigated. The electrical characterization was very encouraging; the sheet resistances of these meshes were lower than those of the conventionally used transparent contacts. The optical transmissions were lower than expected and the causes for the lower measurements have been investigated. The aluminum oxidation, the large metal grain size and the line edge roughness were identified as the main factors of inconsistency and solutions are proposed to improve these shortcomings. The effect of aluminum oxidation was calculated and the passivation of aluminum with SiO2 was evaluated as a solution. A cold deposition of aluminum reduced the aluminum grain size from 60 nm to 20 nm and the roughness from 5 nm to 0.5 nm. Furthermore, replacing the conventional lift-off process by a dry back-etch process led to much smoother metal line edges and much high optical transparency. The optical measurements were consistent with the simulations. Therefore, reduced roughness and smooth metal line edges were found to be especially critical considerations for deep UV application of the meshes.
Show less - Date Issued
- 2011
- Identifier
- CFE0003645, ucf:48893
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003645
