Robustness to misalignment of low-cost, compact quantitative phase imaging architectures.

Non-interferometric approaches to quantitative phase imaging could enable its application in low-cost, miniaturised settings such as capsule endoscopy. We present two possible architectures and both analyse and mitigate the effect of sensor misalignment on phase imaging performance. This is a crucial step towards determining the feasibility of implementing phase imaging in a capsule device. First, we investigate a design based on a folded 4f correlator, both in simulation and experimentally. We demonstrate a novel technique for identifying and compensating for axial misalignment and explore the limits of the approach. Next, we explore the implications of axial and transverse misalignment, and of manufacturing variations on the performance of a phase plate-based architecture, identifying a clear trade-off between phase plate resolution and algorithm convergence time. We conclude that while the phase plate architecture is more robust to misalignment, both architectures merit further development with the goal of realising a low-cost, compact system for applying phase imaging in capsule endoscopy

Robustness to misalignment of low-cost, compact quantitative phase imaging architectures

Non-interferometric approaches to quantitative phase imaging could enable its application in low-cost, miniaturised settings such as capsule endoscopy. We present two possible architectures and both analyse and mitigate the effect of sensor misalignment on phase imaging performance. This is a crucial step towards determining the feasibility of implementing phase imaging in a capsule device. First, we investigate a design based on a folded 4f correlator, both in simulation and experimentally. We demonstrate a novel technique for identifying and compensating for axial misalignment and explore the limits of the approach. Next, we explore the implications of axial and transverse misalignment, and of manufacturing variations on the performance of a phase plate-based architecture, identifying a clear trade-off between phase plate resolution and algorithm convergence time. We conclude that while the phase plate architecture is more robust to misalignment, both architectures merit further development with the goal of realising a low-cost, compact system for applying phase imaging in capsule endoscopy

Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

The Montgomery Thyroplasty Implant System: A 360° Assessment

This thesis provides a 360° assessment of one thyroplasty implant called the Montgomery Thyroplasty Implant System (MTIS).The author made an effort to use alternative and innovative research techniques. The originality lies in the choice of the Pareto technique as literature review, in the technique of the e-mail survey as to the use of voice indicators by practitioner, in a proof-of-concept study of an innovative (perhaps even disruptive) endoscopic measuring technique, and finally in the development of a new concept, the α -ratio with the use of virtual CT scan reconstruction to study the interactions between thyroid cartilage morphology and post-operative voice results.Thesis results can be summarized as follows:Most commonly used Voice Outcome Indicators (VOIs) to determine the effectiveness of surgical Unilateral Vocal Fold Palsy (UVFP) treatment are: Maximum Phonation Time and Voice Handicap Index. Mean Airflow is a VOI deserving further investigations.MTIS is a simple technique, offering permanent results with the possibility of treating posterior glottal gaps in most UVFP configurations.MTIS provides excellent results for male individuals. Female patients have a lower benefit after MTIS. The depth of the implant, as well as cartilage fenestration location, are factors influencing this gender discrepancySoluvos b.v. BESS Group Inc. XION-Medical GmbHLUMC / Geneeskund

INFLUENCE OF THE MIXTURE PREPARATION ON THE COMBUSTION IN DIRECT INJECTION ENGINES

During the last two centuries, the development of the internal combustion engine has followed the evolution of the customer expectations. From the race for pure performances, high power, and fun to drive, perfectly well illustrated by the fabulous Mercedes 300 SL, the focus moved towards fuel efficient engines under the pressure of the still increasing oil prices. The well-known Diesel powertrain, up to this period limited to industrial vehicles, suddenly became the object of many researches, even for automotive manufacturers, specialists for sport cars. Technologic developments, mainly concerning turbocharging and injection, allowed the opening of the passenger cars market to CI engines due to acceptable noise, power and still unreachable efficiency. On the gasoline side, direct injection moved from racing to economic cars by the introduction of the stratified combustion. More recently, the pressure rose for dramatically reducing the air pollution, both in urban areas, by limiting NOx and soot, but also, at the scale of the earth, for managing CO2 rejections and thereby enlarging the efforts on efficiency. The two first combustion systems described in this document are concerning spray guided and air guided design alternatives to obtain a fuel stratification, and thereby operate the gasoline engine without throttling the air intake, aiming at a better fuel efficiency. The first concept, called MID3S, was based on a 3 valve combustion chamber with a large squish area and a high compression ratio over 12; inspired from the May Fireball system, it was developed with a house made high pressure injector operating up to 80 bars with an outwardly opening needle. An ultra-lean flame-able mixture was formed at WOT in the vicinity of the spark plug for different operating points as low as idle, while the maximum performances were quite close to the targeted 37 kW/l. The efficiency was significantly improved compared to a similar MPI engine while CO and HC were quite acceptable. On the contrary, NOx and soot would have to be improved. The robustness of the squish aerodynamic motion was unfortunately balanced by the sensitivity of spray angle and penetration versus the back pressure and thereby late injection timings, creating plug wetting and fouling. The hollow cone structure of the fuel plume was clearly responsible of this behavior, especially because of the effect of the air entrainment inside the spray. An increase of the injection pressure from 30 to 80 bar, and probably upper, would probably reduce this effect. Concerning methodologies, a dedicated cylinder head was designed with two endoscope locations in order to visualize the interaction between spray, air, walls and combustion –or more precisely soot- with a high speed camera operating within visible wavelengths. The spray structure, formed by a succession of ligaments at the surface of the plume, was clearly emphasized in atmospheric conditions. The second design, called K5M, was based on an adjustable high tumble motion generated in the intake port. A swirl injector provided by Siemens and located between the two intake valves of the pent roof chamber, was operated until 80 bar. Mixture preparation was relying on the interaction between the air motion and the spray, the tumble velocity deviating fuel droplets towards the spark plug situated at the center of the chamber. 3D CFD simulation, PIV and LIF visualization techniques on an optical single cylinder engine were used in parallel in order to understand the spatial evolution of the equivalence ratio during the cycle and the ability to operate the engine at WOT, even at part load. At low BMEP and speed, the natural reduction of the tumble intensity might have been followed by a significant reduction of the injection pressure in order to secure an accurate balance between the two momentum energies; unfortunately, both high cycle to cycle aerodynamic fluctuations and a poor spray atomization at 30 bar didn’t allow to achieve an acceptable ignition stability at low loads due to a too lean mixture in the plug vicinity. Protruded electrodes could have been a solution to the problem but their reliable use in serial life was not secured. On the contrary, mid load performances were globally adequate. The third concept is concerning Diesel combustion aiming at very low NOx and soot emissions by using an innovative injection system. The basic idea relies on the use of a quite homogeneous combustion at low load –called Mild HCCI- and on a diffusion controlled one at higher loads. Based on two injections close one of the other in the vicinity of TDC, the Mild HCCI allows to moderate the combustion noise inherent to the premixed burning phase as the fuel injected during the second injection cools down the first combustion; the advantages of very low NOx and soot emissions until around 8 bar BMEP are meanwhile maintained. Above this value, the noise level becomes unacceptable for automotive applications and the come back to a conventional diffusive combustion becomes mandatory. Based on early academic investigations pointing out the positive effect of small nozzle holes associated to high injection pressures in terms of soot via a significant difference between the lift-off length and the liquid penetration length, an innovative injection system was adapted to a conventional combustion chamber. The first conclusion was concerning a significant improvement of the NOx/soot tradeoff at mid and high loads with quite usual EGR rates. This advantage was due to a much better fuel atomization linked to both small holes and high pressures. The second conclusion was related to the possibility to achieve a “0 soot/ 0 NOx” combustion at high loads while very much increasing EGR and air mass flows. In this case, a Lifted Flame Diffusion Controlled combustion was generated, confirming on a scale 1 engine the results obtained in academic conditions. Nevertheless, the use of 3D simulation allowed to demonstrate that mixture preparation was only one part of the result; the location of the different stages of the combustion in a Kamimoto diagram, much away from the NOx and soot peninsula, highlighted the impact of the LTC (Low Temperature Combustion) thermodynamics. Unfortunately, despite these good results, industrially available EGR and air systems are not able to provide the necessary mass flows. Concerning tools, the development steps were followed by intensive spray visualizations for both the liquid and the vapor phases, in conditions closer and closer to the actual engine. These measurements allowed to precisely evaluate the impact of the diameter size, the rail pressure and the oxygen content on the difference between lift-off and liquid lengths. Finally, the importance of coupling investigation tools like visualization and 3D simulation in conditions as close as possible to the actual engine in terms of temperature, pressure and timing –eg the ability to record a complete mixture and combustion cycle- has been emphasized for both future SI and Diesel engines. In particular, the forecasted increase of the rail pressures will lead to re-optimize the different available spray models and eventually to re-adapt them in terms of physical phenomena because of the great variations of the spray velocity and of the Weber number. The presence of cavitation in the nozzle holes will also have to be taken into account as it has a key role versus coking. In conclusion, it is quite clear that the development of stratified gasoline and low emissions Diesel engines will more and more rely on the mixture preparation and on its association with low gas temperatures.Gastaldi, P. (2015). INFLUENCE OF THE MIXTURE PREPARATION ON THE COMBUSTION IN DIRECT INJECTION ENGINES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48534TESI

A continuum robotic platform for endoscopic non-contact laser surgery: design, control, and preclinical evaluation

The application of laser technologies in surgical interventions has been accepted in the clinical domain due to their atraumatic properties. In addition to manual application of fibre-guided lasers with tissue contact, non-contact transoral laser microsurgery (TLM) of laryngeal tumours has been prevailed in ENT surgery. However, TLM requires many years of surgical training for tumour resection in order to preserve the function of adjacent organs and thus preserve the patient’s quality of life. The positioning of the microscopic laser applicator outside the patient can also impede a direct line-of-sight to the target area due to anatomical variability and limit the working space. Further clinical challenges include positioning the laser focus on the tissue surface, imaging, planning and performing laser ablation, and motion of the target area during surgery. This dissertation aims to address the limitations of TLM through robotic approaches and intraoperative assistance. Although a trend towards minimally invasive surgery is apparent, no highly integrated platform for endoscopic delivery of focused laser radiation is available to date. Likewise, there are no known devices that incorporate scene information from endoscopic imaging into ablation planning and execution. For focusing of the laser beam close to the target tissue, this work first presents miniaturised focusing optics that can be integrated into endoscopic systems. Experimental trials characterise the optical properties and the ablation performance. A robotic platform is realised for manipulation of the focusing optics. This is based on a variable-length continuum manipulator. The latter enables movements of the endoscopic end effector in five degrees of freedom with a mechatronic actuation unit. The kinematic modelling and control of the robot are integrated into a modular framework that is evaluated experimentally. The manipulation of focused laser radiation also requires precise adjustment of the focal position on the tissue. For this purpose, visual, haptic and visual-haptic assistance functions are presented. These support the operator during teleoperation to set an optimal working distance. Advantages of visual-haptic assistance are demonstrated in a user study. The system performance and usability of the overall robotic system are assessed in an additional user study. Analogous to a clinical scenario, the subjects follow predefined target patterns with a laser spot. The mean positioning accuracy of the spot is 0.5 mm. Finally, methods of image-guided robot control are introduced to automate laser ablation. Experiments confirm a positive effect of proposed automation concepts on non-contact laser surgery.Die Anwendung von Lasertechnologien in chirurgischen Interventionen hat sich aufgrund der atraumatischen Eigenschaften in der Klinik etabliert. Neben manueller Applikation von fasergeführten Lasern mit Gewebekontakt hat sich die kontaktfreie transorale Lasermikrochirurgie (TLM) von Tumoren des Larynx in der HNO-Chirurgie durchgesetzt. Die TLM erfordert zur Tumorresektion jedoch ein langjähriges chirurgisches Training, um die Funktion der angrenzenden Organe zu sichern und damit die Lebensqualität der Patienten zu erhalten. Die Positionierung des mikroskopis chen Laserapplikators außerhalb des Patienten kann zudem die direkte Sicht auf das Zielgebiet durch anatomische Variabilität erschweren und den Arbeitsraum einschränken. Weitere klinische Herausforderungen betreffen die Positionierung des Laserfokus auf der Gewebeoberfläche, die Bildgebung, die Planung und Ausführung der Laserablation sowie intraoperative Bewegungen des Zielgebietes. Die vorliegende Dissertation zielt darauf ab, die Limitierungen der TLM durch robotische Ansätze und intraoperative Assistenz zu adressieren. Obwohl ein Trend zur minimal invasiven Chirurgie besteht, sind bislang keine hochintegrierten Plattformen für die endoskopische Applikation fokussierter Laserstrahlung verfügbar. Ebenfalls sind keine Systeme bekannt, die Szeneninformationen aus der endoskopischen Bildgebung in die Ablationsplanung und -ausführung einbeziehen. Für eine situsnahe Fokussierung des Laserstrahls wird in dieser Arbeit zunächst eine miniaturisierte Fokussieroptik zur Integration in endoskopische Systeme vorgestellt. Experimentelle Versuche charakterisieren die optischen Eigenschaften und das Ablationsverhalten. Zur Manipulation der Fokussieroptik wird eine robotische Plattform realisiert. Diese basiert auf einem längenveränderlichen Kontinuumsmanipulator. Letzterer ermöglicht in Kombination mit einer mechatronischen Aktuierungseinheit Bewegungen des Endoskopkopfes in fünf Freiheitsgraden. Die kinematische Modellierung und Regelung des Systems werden in ein modulares Framework eingebunden und evaluiert. Die Manipulation fokussierter Laserstrahlung erfordert zudem eine präzise Anpassung der Fokuslage auf das Gewebe. Dafür werden visuelle, haptische und visuell haptische Assistenzfunktionen eingeführt. Diese unterstützen den Anwender bei Teleoperation zur Einstellung eines optimalen Arbeitsabstandes. In einer Anwenderstudie werden Vorteile der visuell-haptischen Assistenz nachgewiesen. Die Systemperformanz und Gebrauchstauglichkeit des robotischen Gesamtsystems werden in einer weiteren Anwenderstudie untersucht. Analog zu einem klinischen Einsatz verfolgen die Probanden mit einem Laserspot vorgegebene Sollpfade. Die mittlere Positioniergenauigkeit des Spots beträgt dabei 0,5 mm. Zur Automatisierung der Ablation werden abschließend Methoden der bildgestützten Regelung vorgestellt. Experimente bestätigen einen positiven Effekt der Automationskonzepte für die kontaktfreie Laserchirurgie

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

NASA Tech Briefs, October 2002

Topics include: a technology focus on sensors, electronic components and systems, software, materials, materials, mechanics, manufacturing, physical sciences, information sciences, book and reports, motion control and a special section of Photonics Tech Briefs

Applications and Experiences of Quality Control

The rich palette of topics set out in this book provides a sufficiently broad overview of the developments in the field of quality control. By providing detailed information on various aspects of quality control, this book can serve as a basis for starting interdisciplinary cooperation, which has increasingly become an integral part of scientific and applied research