Readout electronics for microbolometer infrared focal plane array

Ph.DDOCTOR OF PHILOSOPH

Bolometers

Infrared Detectors and technologies are very important for a wide range of applications, not only for Military but also for various civilian applications. Comparatively fast bolometers can provide large quantities of low cost devices opening up a new era in infrared technologies. This book deals with various aspects of bolometer developments. It covers bolometer material aspects, different types of bolometers, performance limitations, applications and future trends. The chapters in this book will be useful for senior researchers as well as beginning graduate students

Conception, modélisation et caractérisation de détecteurs térahertz innovants

Le but de cette thèse est d établir une modélisation électromagnétique du détecteurbolométrique térahertz (THz). Ce travail aide à faciliter la conception de bolomètre THz dontla structure est basée sur celle de bolomètre infrarouge à température ambiante. Le contextede la thèse est l imagerie THz active. Nous avons étudié le comportement électromagnétiqued un bolomètre à antenne de bande spectrale 1 5 THz. Deux modes de simulation ont étéréalisées : l une est en mode de réception et l autre est d émission. La combinaison de cesmodes de simulation constitue un outil important pour concevoir le bolomètre THz. Latechnique de spectroscopie par transformée de Fourier a été utilisée pour caractériserexpérimentalement le comportement électromagnétique du détecteur. Nous avons mesuré laréflectivité de la surface du plan focal de détecteur ainsi que la réponse spectrale du détecteur.Les deux sont confrontées avec la simulation et elles se trouvent en bon accord. Avec lesconnaissances obtenues des résultats théorique et mesuré, la recherche aide à améliorer desperformances du détecteur actuel. Nous avons aussi proposé un design pour le bolomètre defaible fréquence (850 GHz). Ce dernier ouvre la perspective d emmener la technologie debolomètre d infrarouge vers la bande sous-térahertz où l imagerie est beaucoup plusfavorable.This PhD thesis aims to establish an electromagnetic modeling of the bolometer atterahertz (THz) range that can facilitate the design of the detector from the uncooled infraredbolometer technology. The envisaged application for the detectors lies in active THz imagingat room temperature. We have studied the optical coupling of a THz antenna-coupledbolometer operating in the range 1 5 THz. Simulations in receiving and transmitting modeshave been performed to study the optical characteristics of the bolometer. The combination ofthese two simulation types leads to a powerful toolset to design terahertz bolometers. For theexperimental aspect, measurements have been performed by using Fourier-transformtechnique to study experimentally the electromagnetic behavior of the bolometer. They aremeasurement of reflectivity of the focal plane array s surface and spectral responsemeasurement. The results of measurement were found to be in good agreement with thesimulation. The understanding from the study in this PhD helps us make improvement to theactual detector. Also the design of bolometer for low frequency (850 GHz) has beenproposed. This leads to a perspective of using bolometer for terahertz imaging at thefrequency where many characteristic of the terahertz radiation are favorable for imagingapplication.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Spaceborne sensors (1983-2000 AD): A forecast of technology

A technical review and forecast of space technology as it applies to spaceborne sensors for future NASA missions is presented. A format for categorization of sensor systems covering the entire electromagnetic spectrum, including particles and fields is developed. Major generic sensor systems are related to their subsystems, components, and to basic research and development. General supporting technologies such as cryogenics, optical design, and data processing electronics are addressed where appropriate. The dependence of many classes of instruments on common components, basic R&D and support technologies is also illustrated. A forecast of important system designs and instrument and component performance parameters is provided for the 1983-2000 AD time frame. Some insight into the scientific and applications capabilities and goals of the sensor systems is also given

Uncooled Microbolometer Imaging Systems for Machine Vision

Over the last 20 years, the cost of uncooled microbolometer-based imaging systems has drastically decreased while performance has increased. In the simplest terms, the figure of merit for these types of thermal detectors is given in terms of the τ-NETD product, the combination of the thermal time constant and the noise equivalent temperature difference. Considering these factors, optimal system design parameters are investigated to maximize visual information content. This dissertation focuses on improving scene information in the longwave infrared (LWIR) spectrum that has had its validity and quality degraded by noise, blur, and reflected radiance. Taken together, noise and blur degrade image quality, directly affecting system performance for object detectors trained with deep learning. Representing noise with NETD and blur in terms of equivalent angular resolution, this research provides a systematic method for relating design parameters to specific machine vision tasks that are difficult to define in a traditional imaging sense. This method provides for a system design approach based on information requirements rather than improvements to machine vision algorithms. As a machine vision function, automated target recognition (ATR) has improved with new technologies and the wide proliferation of infrared staring focal planes. Infrared search and track (IRST), which is target detection and localization at long ranges of unresolved targets, can be performed by both photon counting and microbolometer systems. The transition from broadband system design to one that involves spectral characterizations of components provides a better understanding of the performance and capabilities of new technologies. Unlike reflective bands such as visible and shortwave infrared (SWIR), reflected radiance reduces contrast in the LWIR, resulting in lost information. This research considers the sky path radiance contribution to the radiant exitance of a scene that reduces contrast, and consequently, information. Results show that reduced contrast can be overcome by utilizing multiband spectral imaging systems to remove the reflected component, thus increasing the scene information available. In addition, better scene consistency can be achieved between day and night when reflected radiance is removed. The multiband LWIR system designs presented take advantage of the low τ-NETD of modern microbolometers and demonstrate feasibility in future multiband applications

Photodetectors

In this book some recent advances in development of photodetectors and photodetection systems for specific applications are included. In the first section of the book nine different types of photodetectors and their characteristics are presented. Next, some theoretical aspects and simulations are discussed. The last eight chapters are devoted to the development of photodetection systems for imaging, particle size analysis, transfers of time, measurement of vibrations, magnetic field, polarization of light, and particle energy. The book is addressed to students, engineers, and researchers working in the field of photonics and advanced technologies

Development and evaluation of thermal imaging techniques for non-contact respiration monitoring.

Respiration rate is one of the main indicators of an individual's health and therefore it requires accurate quantification. Its value can be used to predict life threatening conditions such as the child death syndrome and heart attacks. The current respiration rate monitoring methods are contact based, i.e. a sensing device needs to be attached to the person's body. Physically constraining infants and young children by a sensing device can be stressful to the individuals which in turn affects their respiration rate. Therefore, measuring respiration rate in a non-contact manner (i.e. without attaching the sensing device to the subject) has distinct benefits. Currently there is not any non-contact respiration rate monitoring available for use in medical field.The aim of this study was to investigate thermal imaging as a means for non-contact respiration rate monitoring. Thermal imaging is safe and easy to deploy. Twenty children were enrolled for the study at Sheffield Children Hospital; the children were from 6 month to 17 years old. They slept comfortably in a bed during the recordings. A high resolution high sensitivity (0.08 degree Kelvin) thermal camera (Flir A40) was used for the recordings. The image capture rate was 50 frames per second and its recording duration per subject was two minutes (i.e. 6000 image frames)A median digital lowpass filter was used to remove unwanted frequency spectrum of the images. An important issue was to localize and track the area centered on the tip of the nose (i.e. respiration region of interest, ROI). A number of approaches were developed for this purpose. The most effective approach was to identify use the warmest facial point (i.e. the point where the bridge of the nose meets the corner of one of the eyes). A novel method to analyse the selected ROI was devised. This involved segmenting the ROI into eight equal segments centred on the tip of nose. A respiration signal was produced for each segment across the 6000 recorded images from each subject. The study demonstrated that the process of dividing the ROI into eight segments improves determination of respiration rate. The respiration signals were processed both in the time and frequency domains to determine respiration rates for the 20 subjects included in the study. The respiration values obtained from the two domains were close. During each recording respiration rate was monitored using conventional contact methods (e.g. nostril thermistor, abdomen and chest movement sensor etc). There was a close correlation (correlation value 0.99) between respiration values obtained by thermal imaging and those obtained using conventional contact method.The novel aspects of the study relate to the development of techniques that facilitated thermal imaging as an effective non-contact respiration rate monitoring in both normal and patient subject groups

Imaging by Detection of Infrared Photons Using Arrays of Uncooled Micromechanical Detectors

The objective of this dissertation was to investigate the possibility of uncooled infrared imaging using arrays of optically-probed micromechanical detectors. This approach offered simplified design, improved reliability and lower cost, while attaining the performance approaching that contemporary uncooled imagers. Micromechanical infrared detectors undergo deformation due to the bimetallic effect when they absorb infrared photons. The performance improvements were sought through changes in structural design such as modification and simplification of detector geometry as well as changes in the choice of materials. Detector arrays were designed, fabricated and subsequently integrated into the imaging system and relevant parameters, describing the sensitivity and signal-to-noise ratio, were characterized. The values of these parameters were compared to values published for other uncooled micromechanical detectors and commercial uncooled detectors. Several designs have been investigated. The first design was made of standard materials for this type of detectors - silicon nitride and gold. The design utilized changes in detector geometry such as reduction in size and featured an optical resonant cavity between the detector and the substrate on which arrays were built. This design provided decrease in levels of noise equivalent temperature difference (NETD) to as low as 500 mK. The NETD parameter limits the lowest temperature gradient on the imaged object that can be resolved by the imaging device. The second design used silicon dioxide and aluminum, materials not yet fully investigated. It featured a removed substrate beneath each detector in the array, to allow unobstructed transmission of incoming IR radiation and improve the thermal isolation of the detector. Second design also featured an amorphous silicon layer between silicon dioxide and aluminum layers, to serve as an optical resonant cavity. The NETD levels as low as 120 mK have been achieved. The only difference between the third and the second design was the modification of the geometry to minimize the noise. Successfully obtained thermal images and improved NETD values, approaching those of modern uncooled imagers (20 mK for commercial bolometer-based detectors), confirm the viability of this approach. With further improvements, this approach has a potential of becoming a lowcost alternative for uncooled infrared imaging

Passive terahertz imaging with lumped element kinetic inductance detectors

Progress towards large format, background limited detector arrays in and around the terahertz or sub-millimetre region of the electromagnetic spectrum has – until recently – been hampered by the complexities in fabrication and cryogenic electronic readout associated with increasing pixel counts. Kinetic inductance detectors or KIDs are a superconducting pair breaking detector technology designed to overcome these complexities. Traditionally, KID arrays have been developed for imaging in astronomy. However, the high sensitivities, broadband responses, fast time constants and high detector counts that are achievable – along with the simplicity of fabrication and readout compared to other contemporary technologies – make them suitable (and in fact desirable) for a variety of applications. This thesis documents the development of a concept instrument to demonstrate KID technology for general purpose imaging applications. Specifically, I present the design, construction and performance of a near background limited, quasi-video rate, passive imaging system based on arrays of Aluminium lumped-element KIDs. The camera operates in two atmospheric windows at 150 GHz (2 mm) and 350GHz (850 μm) with 60 and 152 pixels, respectively. Array fabrication was achieved with a single photolithographic cycle of thin film deposition, patterning and etching. Full array readout is with a single cryogenic amplifier and room temperature FPGA based frequency domain multiplexing electronics. The camera is the first of its kind in applying KID arrays to imaging systems outside of pure astrophysics research and is the result of efforts from the staff and students of the Astronomy Instrumentation Group (AIG) in the School of Physics and Astronomy with support from QMC Instruments Ltd. The system exemplifies the AIG’s world-leading expertise in the development of far-infrared/sub-mm instrumentation as well as QMCI’s vision to provide the highest quality terahertz optical components and detector systems to the global marketplace