Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications

Liquid Crystal on Silicon (LCoS) has become one of the most widespread technologies for spatial light modulation in optics and photonics applications. These reflective microdisplays are composed of a high-performance silicon complementary metal oxide semiconductor (CMOS) backplane, which controls the light-modulating properties of the liquid crystal layer. State-of-the-art LCoS microdisplays may exhibit a very small pixel pitch (below 4 ?m), a very large number of pixels (resolutions larger than 4K), and high fill factors (larger than 90%). They modulate illumination sources covering the UV, visible, and far IR. LCoS are used not only as displays but also as polarization, amplitude, and phase-only spatial light modulators, where they achieve full phase modulation. Due to their excellent modulating properties and high degree of flexibility, they are found in all sorts of spatial light modulation applications, such as in LCOS-based display systems for augmented and virtual reality, true holographic displays, digital holography, diffractive optical elements, superresolution optical systems, beam-steering devices, holographic optical traps, and quantum optical computing. In order to fulfil the requirements in this extensive range of applications, specific models and characterization techniques are proposed. These devices may exhibit a number of degradation effects such as interpixel cross-talk and fringing field, and time flicker, which may also depend on the analog or digital backplane of the corresponding LCoS device. The use of appropriate characterization and compensation techniques is then necessary

Image Restoration for Remote Sensing: Overview and Toolbox

Remote sensing provides valuable information about objects or areas from a distance in either active (e.g., RADAR and LiDAR) or passive (e.g., multispectral and hyperspectral) modes. The quality of data acquired by remotely sensed imaging sensors (both active and passive) is often degraded by a variety of noise types and artifacts. Image restoration, which is a vibrant field of research in the remote sensing community, is the task of recovering the true unknown image from the degraded observed image. Each imaging sensor induces unique noise types and artifacts into the observed image. This fact has led to the expansion of restoration techniques in different paths according to each sensor type. This review paper brings together the advances of image restoration techniques with particular focuses on synthetic aperture radar and hyperspectral images as the most active sub-fields of image restoration in the remote sensing community. We, therefore, provide a comprehensive, discipline-specific starting point for researchers at different levels (i.e., students, researchers, and senior researchers) willing to investigate the vibrant topic of data restoration by supplying sufficient detail and references. Additionally, this review paper accompanies a toolbox to provide a platform to encourage interested students and researchers in the field to further explore the restoration techniques and fast-forward the community. The toolboxes are provided in https://github.com/ImageRestorationToolbox.Comment: This paper is under review in GRS

Multi-wavelength infrared imaging computer systems and applications

This dissertation presents the development of three computer systems for multi-wavelength thermal imaging. Two computer systems were developed for the multi-wavelength imaging pyrometers (M-WIPs) that yield non-contact temperature measurements by remotely sensing the surface of objects with unknown wavelength-dependent emissivity. These M-WIP computer systems represent the state-of-art development in remote temperature measurement system based on the multi-wavelength approach. The dissertation research includes M-WIP computer system integration, software development, performance evaluation, and also applications in monitoring and control of temperature distribution of silicon wafers in a rapid thermal process system. The two M-WIPs are capable of data acquisition, signal processing, system calibration, radiometric measurement, parallel processing and process control. Temperature measurement experiments demonstrated the accuracy of ±1°C against blackbody and ±4°C for colorbody objects. Various algorithms were developed and implemented, including real-time two-point non-uniformity correction, thermal image pseudocoloring, PC to SUN workstation data transfer, automatic IR camera integration time control, and radiometric measurement parallel processing. A third computer system was developed for the demonstration of a 3-color InGaAs FPA which can provide images with information in three different IR wavelength range simultaneously. Numbers of functions were developed to demonstrate and characterize 3-color FPAs, and the system was delivered to be used by the 3-color FPA manufacturer

Fast Objective Coupled Planar Illumination Microscopy

Among optical imaging techniques light sheet fluorescence microscopy stands out as one of the most attractive for capturing high-speed biological dynamics unfolding in three dimensions. The technique is potentially millions of times faster than point-scanning techniques such as two-photon microscopy. This potential is especially poignant for neuroscience applications due to the fact that interactions between neurons transpire over mere milliseconds within tissue volumes spanning hundreds of cubic microns. However current-generation light sheet microscopes are limited by volume scanning rate and/or camera frame rate. We begin by reviewing the optical principles underlying light sheet fluorescence microscopy and the origin of these rate bottlenecks. We present an analysis leading us to the conclusion that Objective Coupled Planar Illumination (OCPI) microscopy is a particularly promising technique for recording the activity of large populations of neurons at high sampling rate. We then present speed-optimized OCPI microscopy, the first fast light sheet technique to avoid compromising image quality or photon efficiency. We enact two strategies to develop the fast OCPI microscope. First, we devise a set of optimizations that increase the rate of the volume scanning system to 40 Hz for volumes up to 700 microns thick. Second, we introduce Multi-Camera Image Sharing (MCIS), a technique to scale imaging rate by incorporating additional cameras. MCIS can be applied not only to OCPI but to any widefield imaging technique, circumventing the limitations imposed by the camera. Detailed design drawings are included to aid in dissemination to other research groups. We also demonstrate fast calcium imaging of the larval zebrafish brain and find a heartbeat-induced motion artifact. We recommend a new preprocessing step to remove the artifact through filtering. This step requires a minimal sampling rate of 15 Hz, and we expect it to become a standard procedure in zebrafish imaging pipelines. In the last chapter we describe essential computational considerations for controlling a fast OCPI microscope and processing the data that it generates. We introduce a new image processing pipeline developed to maximize computational efficiency when analyzing these multi-terabyte datasets, including a novel calcium imaging deconvolution algorithm. Finally we provide a demonstration of how combined innovations in microscope hardware and software enable inference of predictive relationships between neurons, a promising complement to more conventional correlation-based analyses

Tapered gain guides in diode lasers and picosecond Q-switched bow tie laser arrays

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN025356 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Improving SLI Performance in Optically Challenging Environments

The construction of 3D models of real-world scenes using non-contact methods is an important problem in computer vision. Some of the more successful methods belong to a class of techniques called structured light illumination (SLI). While SLI methods are generally very successful, there are cases where their performance is poor. Examples include scenes with a high dynamic range in albedo or scenes with strong interreflections. These scenes are referred to as optically challenging environments. The work in this dissertation is aimed at improving SLI performance in optically challenging environments. A new method of high dynamic range imaging (HDRI) based on pixel-by-pixel Kalman filtering is developed. Using objective metrics, it is show to achieve as much as a 9.4 dB improvement in signal-to-noise ratio and as much as a 29% improvement in radiometric accuracy over a classic method. Quality checks are developed to detect and quantify multipath interference and other quality defects using phase measuring profilometry (PMP). Techniques are established to improve SLI performance in the presence of strong interreflections. Approaches in compressed sensing are applied to SLI, and interreflections in a scene are modeled using SLI. Several different applications of this research are also discussed

Image Sensor Nonuniformity Correction by a Scene-Based Maximum Likelihood Approach

Image sensors come with a spatial inhomogeneity, known as Fixed Pattern Noise or image sensor nonuniformity, which degrades the image quality. These nonuniformities are regarded as the systematic errors of the image sensor, however, they change with the sensor temperature and with time. This makes laboratory calibrations unsatisfying. Scene based nonuniformity correction methods are therefore necessary to correct for these sensor errors. In this thesis, a new maximum likelihood estimation method is developed that estimates a sensor’s nonuniformities from a given set of input images. The method follows a rigorous mathematical derivation that exploits the available sensor statistics and uses only well-motivated assumptions. While previous methods need to optimize a free parameter, the new method’s parameters are defined by the statistics of the input data. Furthermore, the new method reaches a better performance than the previous methods. Specialized developments that include a row- or column-wise and a combined estimation of the nonuniformity parameters are introduced as well and are of relevance for typical industrial applications. Finally it is shown that the previous methods can be regarded as simplifications of the newly developed method. This deliberation gives a new view onto the problem of scene based nonuniformity estimation and allows to select the best method for a given application

A CCD based curvature wavefront sensor for Adaptive Optics in Astronomy

Adaptive Optik (AO) ist eine Technik, um Störungen in der Abbildung von Objekten im Teleskop auszugleichen. Diese Störungen werden von Fluktuationen des Brechungsindexes in der Erdatmosphäre hervorgerufen. Zum Messen dieser Störungen gibt es eine Reihe verschiedener Wellenfrontsensoren. Einer davon ist der 'Curvature'- Wellenfrontsensor, was soviel wie 'Krümmungs'- Wellenfrontsensor bedeutet. An der Europäischen Südsternwarte (ESO) in Garching werden für das Very Large Telescope (VLT) und das VLT Interferometer (VLTI) eine Reihe von adaptiven Optiksystemen entwickelt, die den Curvature - Wellenfrontsensor verwenden. Bisher wurden in Curvature AO-Systemen Avalanche Photodioden (APDs) als Detektoren verwendet, da sehr kurze Belichtungszeiten (200 Mikrosekunden) und ein sehr niedriges Ausleserauschen des Detektors nötig sind. Aufgrund von Fortschritten in der Herstellungstechnologie von Charge Coupled Devices (CCDs) entwickelten wir ein spezielles CCD und untersuchten dessen Leistungsfähigkeit für ein 60 Element Curvature AO System, das mit sehr schwachen Lichtsignalen arbeitet. Hier wurde erstmals ein CCD als Wellenfrontsensor verwendet. Diese Dissertation zeigt, daß ein CCD annäherend die gleiche Leistungsfähigkeit wie APDs bietet, jedoch zu einem Bruchteil der Kosten und geringerer Komplexität. Weiter hat das CCD eine höhere Quantenausbeute und einen größeren dynamischen Bereich als APDs. Ein Ausleserauschen von weniger als 1,5 Elektronen bei 4000 Bildern pro Sekunde wurde erreicht. Für AO Systeme, die Wellenfrontkorrekturen mit vielen Elementen durchführen, können dünne, von hinten beleuchtete CCDs, APDs als bessere Detektoren ersetzen. Diese Dissertation präsentiert das Konzept, das Design und die Bestimmung der Leistungsfähigkeit dieses CCDs. Erste (von vorne beleuchtete) CCDs wurden erfolgreich getestet und die Leistungsfähigkeit in einem Laborexperiment nachgewiesen