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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Infrared based monocular relative navigation for active debris removal

Yilmaz, Özgün January 2018 (has links)
In space, visual based relative navigation systems suffer from the harsh illumination conditions of the target (e.g. eclipse conditions, solar glare, etc.). In current Rendezvous and Docking (RvD) missions, most of these issues are addressed by advanced mission planning techniques (e.g strict manoeuvre timings). However, such planning would not always be feasible for Active Debris Removal (ADR) missions which have more unknowns. Fortunately, thermal infrared technology can operate under any lighting conditions and therefore has the potential to be exploited in the ADR scenario. In this context, this study investigates the benefits and the challenges of infrared based relative navigation. The infrared environment of ADR is very much different to that of terrestrial applications. This study proposes a methodology of modelling this environment in a computationally cost effective way to create a simulation environment in which the navigation solution can be tested. Through an intelligent classification of possible target surface coatings, the study is generalised to simulate the thermal environment of space debris in different orbit profiles. Through modelling various scenarios, the study also discusses the possible challenges of the infrared technology. In laboratory conditions, providing the thermal-vacuum environment of ADR, these theoretical findings were replicated. By use of this novel space debris set-up, the study investigates the behaviour of infrared cues extracted by different techniques and identifies the issue of short-lifespan features in the ADR scenarios. Based on these findings, the study suggests two different relative navigation methods based on the degree of target cooperativeness: partially cooperative targets, and uncooperative targets. Both algorithms provide the navigation solution with respect to an online reconstruction of the target. The method for partially cooperative targets provides a solution for smooth trajectories by exploiting the subsequent image tracks of features extracted from the first frame. The second algorithm is for uncooperative targets and exploits the target motion (e.g. tumbling) by formulating the problem in terms of a static target and a moving map (i.e. target structure) within a filtering framework. The optical flow information is related to the target motion derivatives and the target structure. A novel technique that uses the quality of the infrared cues to improve the algorithm performance is introduced. The problem of short measurement duration due to target tumbling motion is addressed by an innovative smart initialisation procedure. Both navigation solutions were tested in a number of different scenarios by using computer simulations and a specific laboratory set-up with real infrared camera. It is shown that these methods can perform well as the infrared-based navigation solutions using monocular cameras where knowledge relating to the infrared appearance of the target is limited.
42

An adaptive near-infrared illuminator for outdoor face recognition. / 用於戶外人臉辨識的近紅外線適應性照明 / Yong yu hu wai ren lian bian shi de jin hong wai xian shi ying xing zhao ming

January 2010 (has links)
Cheung, Siu Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 81-86). / Abstracts in English and Chinese. / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- Introduction to Face Recognition --- p.2 / Chapter 1.1.1. --- Modes of Face Recognition --- p.2 / Chapter 1.1.2. --- Typical Face Recognition System --- p.3 / Chapter 1.1.3. --- Face Recognition Algorithms --- p.4 / Chapter 1.1.4. --- The State of the Art --- p.5 / Chapter 1.2. --- Outdoor Face Recognition --- p.6 / Chapter 1.2.1. --- The Outdoor Environment --- p.6 / Chapter 1.2.2. --- The Illumination Variation Problem in the Outdoors --- p.8 / Chapter 1.3. --- Related works --- p.10 / Chapter 1.3.1. --- Face Appearance Modeling --- p.10 / Chapter 1.3.2. --- Illumination Invariant Features and Representations --- p.13 / Chapter 1.3.3. --- Active Near-Infrared Illumination --- p.14 / Chapter 1.4. --- Proposed method --- p.17 / Chapter 1.5. --- Design Requirements --- p.18 / Chapter 2. --- COMPENSATION METHODOLOGY FOR OUTDOOR FACE RECOGNITION --- p.20 / Chapter 2.1. --- Illumination from the Sun --- p.21 / Chapter 2.2. --- Effect of Sunlight Illumination --- p.22 / Chapter 2.3. --- A Compensation Model --- p.24 / Chapter 2.4. --- A Face Lighting Simulator --- p.28 / Chapter 2.4.1. --- Face 3D Models --- p.29 / Chapter 2.4.2. --- Light Sources --- p.30 / Chapter 2.4.3. --- Synthesis of Face Image --- p.31 / Chapter 2.5. --- Simulation Results --- p.32 / Chapter 2.5.1. --- Optimum Compensation Angles --- p.33 / Chapter 2.5.2. --- Effect of Illuminator Intensity --- p.36 / Chapter 2.5.3. --- Effect of Illuminator Elevation Angle --- p.38 / Chapter 2.5.4. --- Effect of Sunlight Elevation Angle --- p.41 / Chapter 2.5.5. --- Illumination from Both Sides --- p.42 / Chapter 2.6. --- Summary --- p.43 / Chapter 3. --- AN ADAPTIVE ILLUMINATOR --- p.45 / Chapter 3.1. --- Hardware Design --- p.45 / Chapter 3.1.1. --- Near-infrared Camera --- p.45 / Chapter 3.1.2. --- Illumination Panels --- p.48 / Chapter 3.1.3. --- Illuminator Controller --- p.56 / Chapter 3.1.4. --- Illumination Characteristics --- p.59 / Chapter 3.2. --- Algorithms --- p.62 / Chapter 3.2.1. --- Light Balance Estimation --- p.63 / Chapter 4. --- EXPERIMENTS AND RESULTS --- p.67 / Chapter 4.1. --- Effect of compensation angle on face similarity --- p.68 / Chapter 4.2. --- Effect of illumination compensation under different sunlight conditions --- p.71 / Chapter 4.3. --- Impact on recognition performance --- p.72 / Chapter 5. --- CONCLUSIONS --- p.76 / Chapter 6. --- BIBLIOGRAPHY --- p.81
43

Heat Transfer in a Rotary Drum Using Infrared Camera Temperature Measurement

January 2019 (has links)
abstract: Rotary drums are commonly used for their high heat and mass transfer rates in the manufacture of cement, pharmaceuticals, food, and other particulate products. These processes are difficult to model because the particulate behavior is governed by the process conditions such as particle size, particle size distribution, shape, composition, and operating parameters, such as fill level and rotation rate. More research on heat transfer in rotary drums will increase operating efficiency, leading to significant energy savings on a global scale. This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2019
44

Modeling of the orientation dependence of scanned HgCdTe infrared detectors

Reudink, Mark D. 19 December 1991 (has links)
Mercury cadmium telluride is important in the detection of electromagnetic radiation in the eight to twelve micron atmospheric window for infrared imaging systems. High resolution infrared imaging systems use either large (256x256 element to 1024x1024 element) staring arrays or much smaller (1-6 element) scanned arrays in which the image is optically scanned across the detectors. In scanned arrays, high resolution and sensitivity may result in the scan direction not being parallel to the detector bias current. The response of an infrared detector to uniform illumination is investigated. It is found that variations in the detector thickness result in significant changes in output voltage. Scanned detectors are modeled in five different orientations; scan parallel to bias, scan opposite to bias, scan perpendicular to bias, and two orientations of the scan diagonal to the bias. The response is analyzed for two cases: 1) the size of the scanned radiation equal to the size of the detector and 2) when the pixel width is half of the width of the detector, but of equal length. Results of the simulation show that the fastest response occurs when the scan and bias are parallel. The largest response occurs when the scan direction is diagonal to the bias, but the response time is much slower than when the bias is parallel to the scan. Therefore, a tradeoff must be made between maximum signal and speed of response. Test detectors are being fabricated and will be tested at FLIR Systems Inc., Portland, Oregon, to confirm the model predictions. / Graduation date: 1992
45

Hybrid Organic/Inorganic Optical Upconversion Devices

Chen, Jun 13 December 2011 (has links)
The widely available charge coupled device (CCD) and lately CMOS imaging devices have created many applications on a mass scale. However these devices are limited to wavelengths shorter than about 1 μm. Hybrid photon upconversion devices have been developed recently. The end goal is to achieve an alternative technology for imaging in the 1.5-μm region. The hybrid upconversion idea relies on the integration of a photodetector and an organic light emitting diode (OLED). Under a forward bias for the OLED, the detected signal in the Photodetector is sent to the OLED, resulting in an increase in emission at a shorter wavelength and therefore achieving optical up conversion. An OLED device can simply consists of a stack of anode, a hole transport layer (HTL), a light-emitting layer, an electron transport layer (ETL), a cathode layer, and it typically emits visible light. As each organic molecule is a topologically perfect structure, the growth of each organic layer does not require “lattice matching”, which has been the fundamental limit for inorganic semiconductor monolithic devices. Thus, integration of an OLED with a III–V compound semiconductor is a highly feasible and desirable approach for making low-cost, large-area, potentially high efficiency devices. This thesis addresses the physics, fabrication and characterization of hybrid near infrared optical upconverters and their imaging application. Firstly, one novel hybrid optical upconverter structure is presented, which substantially improves the upconversion efficiency by embedding a metal mirror. Efficient carrier injection from the inorganic photodetector to the OLED is achieved by the insertion of a thin Au metal embedded mirror at the inorganic-organic interface. The upconversion efficiency was improved by more than 100%. Secondly, the overall upconversion efficiency can be increased significantly, by introducing a gain mechanism into the Photodetector section of the upconverter. A promising option to implement gain is a heterojunction phototransistor (HPT). An InGaAs-InP HPT was integrated with an OLED, which converts 1.5-μm Infrared light to visible light with a built-in electrical gain (~94). The overall upconversion efficiency was improved to be 1.55 W/W. Thirdly, this upconversion approach can also be used to realize a pixelless imaging device. A pixelless hybrid upconversion device consists of a large-area single-mesa device, where the OLED output is spatially correlated with the input 1.5-µm scene. Only the parts receiving incoming photons will emit output photons. To achieve this functionality, photon-generated carriers must flow mainly along the layer-growth direction when injected from the InGaAs light absorption layer into OLED light emission layer. A prototype of pixelless imaging device based on an i-In0.53Ga0.47As/C60 heterojunction was demonstrated, which minimized lateral current spreading. This thesis presents experimental results of the first organic/inorganic hybrid optical amplifer and the first hybrid near infrared imaging device.
46

Hybrid Organic/Inorganic Optical Upconversion Devices

Chen, Jun 13 December 2011 (has links)
The widely available charge coupled device (CCD) and lately CMOS imaging devices have created many applications on a mass scale. However these devices are limited to wavelengths shorter than about 1 μm. Hybrid photon upconversion devices have been developed recently. The end goal is to achieve an alternative technology for imaging in the 1.5-μm region. The hybrid upconversion idea relies on the integration of a photodetector and an organic light emitting diode (OLED). Under a forward bias for the OLED, the detected signal in the Photodetector is sent to the OLED, resulting in an increase in emission at a shorter wavelength and therefore achieving optical up conversion. An OLED device can simply consists of a stack of anode, a hole transport layer (HTL), a light-emitting layer, an electron transport layer (ETL), a cathode layer, and it typically emits visible light. As each organic molecule is a topologically perfect structure, the growth of each organic layer does not require “lattice matching”, which has been the fundamental limit for inorganic semiconductor monolithic devices. Thus, integration of an OLED with a III–V compound semiconductor is a highly feasible and desirable approach for making low-cost, large-area, potentially high efficiency devices. This thesis addresses the physics, fabrication and characterization of hybrid near infrared optical upconverters and their imaging application. Firstly, one novel hybrid optical upconverter structure is presented, which substantially improves the upconversion efficiency by embedding a metal mirror. Efficient carrier injection from the inorganic photodetector to the OLED is achieved by the insertion of a thin Au metal embedded mirror at the inorganic-organic interface. The upconversion efficiency was improved by more than 100%. Secondly, the overall upconversion efficiency can be increased significantly, by introducing a gain mechanism into the Photodetector section of the upconverter. A promising option to implement gain is a heterojunction phototransistor (HPT). An InGaAs-InP HPT was integrated with an OLED, which converts 1.5-μm Infrared light to visible light with a built-in electrical gain (~94). The overall upconversion efficiency was improved to be 1.55 W/W. Thirdly, this upconversion approach can also be used to realize a pixelless imaging device. A pixelless hybrid upconversion device consists of a large-area single-mesa device, where the OLED output is spatially correlated with the input 1.5-µm scene. Only the parts receiving incoming photons will emit output photons. To achieve this functionality, photon-generated carriers must flow mainly along the layer-growth direction when injected from the InGaAs light absorption layer into OLED light emission layer. A prototype of pixelless imaging device based on an i-In0.53Ga0.47As/C60 heterojunction was demonstrated, which minimized lateral current spreading. This thesis presents experimental results of the first organic/inorganic hybrid optical amplifer and the first hybrid near infrared imaging device.
47

Real-time dynamic infrared scene generation fidelity enhancement /

Sills, Timothy Glenn. Unknown Date (has links)
Computing equipment is fundamental to modern day simulation. Visualisation systems are often the most important component. These produce a representation of the real world in the form of pixels. These pixels are presented to viewers and/or devices under test. / The real world is mathematically treated as continuous domain. Visualisation systems produce pixels that collectively provide a digital representation of the real world. Hence, there are difficulties with using visualisation systems to represent the real world. / Sampling processes are employed for the production of pixels in visualisation systems no matter what the graphics architecture. Considering scene content, if the sample frequency does not meet or exceed the Nyquist frequency, aliasing or spectral folding will be produced. This aliasing may be both spatial and temporal, and can be analysed in both the spatial and spatial frequency domains. Spatial aliasing manifests itself in the form of image artefacts including scene-dependent noise. Temporal aliasing manifests itself in the form of pixel scintillation. Both forms are detrimental to simulation with the degree of detriment depending on the application. For virtual urban warfare simulation, soldiers may experience motion sickness, depending on the quantity and strength of the image artefacts. For simulation of imaging missile engagements, erroneous performance results may be produced due to false cueing information from inadequate object representation. / The Defence Science & Technology Organisation (DSTO) is developing an imaging infrared missile simulation capability. A core component is production of infrared scenes using a visualisation system. This system is designed to generate the best possible scenes for the visible band of the electromagnetic spectrum, making generation of the infrared equivalent somewhat difficult. For example, colour-shading calculations are designed for the visible domain and encoded into hardware. This makes it difficult to generate infrared scenes since the colour-shading calculations might have to be written from scratch, performed outside the graphics hardware then applied to pixels. This is a secondary problem however. / The primary DSTO requirement is that the missile simulation capability provide for realistic object representations at long-distances. Compared to the equivalent within the visual band of the electromagnetic spectrum, the seeker must be presented with scenes that are characterised by much larger dynamic range, using objects with smaller features of interest. The visualisation system sample frequency is therefore insufficient for accurate generation of infrared scenes since the objects are positioned at distances beyond what may be considering normal operating range. The resultant undersampling produces significant spatial and temporal aliasing, resulting in spatial artefacts and pixel scintillation, increasing with object range. This problem must be addressed before any other since undersampling has the potential to render infrared scenes totally erroneous at longer distances. / This research describes the work that has been completed to address the undersampling problem of infrared scene generation on visualisation systems. The overall aim was to address the problem for two types of objects: hard body objects such as airframes, and dynamic objects such as engine exhaust plumes and off-board aircraft countermeasures. The problem was addressed for both types of objects in both a pre- and post-pixelation manner, i.e. before and after the generation of spatial and temporal artefacts. The outcome has been successful, resulting in new anti-aliasing schemes for infrared scene generation on commercial visualisation systems. / Thesis ([PhDInformationTechnology])--University of South Australia, 2004.
48

Rainfall estimation from satellite infrared imagery using artificial neural networks

Hsu, Kuo-lin, January 1996 (has links) (PDF)
Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 228-234).
49

Synthetic image generator model : application of specular and diffuse reflectivity components and performance evaluation in the visible region /

Stark, Richard B. January 1993 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaves 161-163).
50

Preliminary steps towards improving short-term QPF using AIRS observations through 4D-Var data assimilation

Carrier, Matthew J. Zou, Xiaolei. January 2004 (has links)
Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Xiaolei Zou, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Jan. 12, 2005). Includes bibliographical references.

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