Characterization of a Low-Cost Optical Flow Sensor When Using an External Laser as a Direct Illumination Source

In this paper, a low cost optical flow sensor is combined with an external laser device to measure surface displacements and mechanical oscillations. The measurement system is based on applying coherent light to a diffuser surface and using an optical flow sensor to analyze the reflected and transferred light to estimate the displacement of the surface or the laser spot. This work is focused on the characterization of this measurement system, which can have the optical flow sensor placed at different angles and distances from the diffuser surface. The results have shown that the displacement of the diffuser surface is badly estimated when the optical mouse sensor is placed in front of the diffuser surface (angular orientation >150°) while the highest sensitivity is obtained when the sensor is located behind the diffuser surface and on the axis of the laser source (angular orientation 0°). In this case, the coefficient of determination of the measured displacement, R2, was very high (>0.99) with a relative error of less than 1.29%. Increasing the distance between the surface and the sensor also increased the sensitivity which increases linearly, R2 = 0.99. Finally, this measurement setup was proposed to measure very low frequency mechanical oscillations applied to the laser device, up to 0.01 Hz in this work. The results have shown that increasing the distance between the surface and the optical flow sensor also increases the sensitivity and the measurement range

Integrated 3D Hydrogel Waveguide Out-Coupler by Step-and-Repeat Thermal Nanoimprint Lithography: A Promising Sensor Device for Water and pH

Hydrogel materials offer many advantages for chemical and biological sensoring due to their response to a small change in their environment with a related change in volume. Several designs have been outlined in the literature in the specific field of hydrogel-based optical sensors, reporting a large number of steps for their fabrication. In this work we present a three-dimensional, hydrogel-based sensor the structure of which is fabricated in a single step using thermal nanoimprint lithography. The sensor is based on a waveguide with a grating readout section. A specific hydrogel formulation, based on a combination of PEGDMA (Poly(Ethylene Glycol DiMethAcrylate)), NIPAAm (N-IsoPropylAcrylAmide), and AA (Acrylic Acid), was developed. This stimulus-responsive hydrogel is sensitive to pH and to water. Moreover, the hydrogel has been modified to be suitable for fabrication by thermal nanoimprint lithography. Once stimulated, the hydrogel-based sensor changes its topography, which is characterised physically by AFM and SEM, and optically using a specific optical set-up

Payload characterization for CubeSat demonstration of MEMS deformable mirrors

Coronagraphic space telescopes require wavefront control systems for high-contrast imaging applications such as exoplanet direct imaging. High-actuator-count MEMS deformable mirrors (DM) are a key element of these wavefront control systems yet have not been flown in space long enough to characterize their on-orbit performance. The MEMS Deformable Mirror CubeSat Testbed is a conceptual nanosatellite demonstration of MEMS DM and wavefront sensing technology. The testbed platform is a 3U CubeSat bus. Of the 10 x 10 x 34.05 cm (3U) available volume, a 10 x 10 x 15 cm space is reserved for the optical payload. The main purpose of the payload is to characterize and calibrate the onorbit performance of a MEMS deformable mirror over an extended period of time (months). Its design incorporates both a Shack Hartmann wavefront sensor (internal laser illumination), and a focal plane sensor (used with an external aperture to image bright stars). We baseline a 32-actuator Boston Micromachines Mini deformable mirror for this mission, though the design is flexible and can be applied to mirrors from other vendors. We present the mission design and payload architecture and discuss experiment design, requirements, and performance simulations.United States. National Aeronautics and Space Administration (Space Technology Research Fellowship

Enabling and understanding nanoparticle surface binding assays with interferometric imaging

There is great need of robust and high throughput techniques for accurately measuring the concentration of nanoparticles in a solution. Microarray imaging techniques using widely used to quantify the binding of labeled analytes to a functionalized surface. However, most approaches require the combined output of many individual binding events to produce a measurable signal, which limits the sensitivity of such assays at low sample concentrations. Although a number of high-NA optical techniques have demonstrated the capability of imaging individual nanoparticles, these approaches have not been adopted for diagnostics due complex instrumentation and low assay throughput. Alternatively, interferometric imaging techniques based on light scattering have demonstrated the potential for single nanoparticle detection on a robust and inexpensive platform. This dissertation focuses on the development of methods and infrastructure to enable the development of diagnostic assays using the Single Particle Interferometric Imaging Sensor (SP-IRIS). SP-IRIS uses a bright-field reflectance microscope to image microarrays immobilized on a simple reflective substrate, which acts as a common-path homodyne interferometer to enhance the visibility of nanoparticles captured near its surface. This technique can be used to detect natural nanoparticles (such as viruses and exosomes) as well as molecular analytes (proteins and nucleic acid sequences) which have been tagged with metallic nanoparticle in a sandwich assay format. Although previous research efforts have demonstrated the potential for SP-IRIS assays in a variety of applications, these studies have largely been focused on demonstrating theoretical proof of concept in a laboratory setting. In contrast, the effective use of SP-IRIS as a clinical diagnostic platform will require significant functional improvements in automation of assay incubation, instrument control, and image analysis. In this dissertation, we discuss the development of instrumentation and software to support the translation of SP-IRIS from manual laboratory technique into an automated diagnostic platform. We first present a collection of mechanical solutions to enable the real-time, in-solution imaging of nanoparticles in disposable microfluidic cartridges. Next, we present image analysis techniques for the detection of nanoparticle signatures within digital images, and discuss solutions to the unique obstacles presented by the ill-defined focal properties of homodyne interferometry. Finally, we present a particle tracking algorithm for residence time analysis of nanoparticle binding in real-time datasets. Collectively, these improvements represent significant progress towards the use of SP-IRIS as a robust and automated diagnostic platform.2019-07-02T00:00:00

ANALYSIS OF LASER POWER CONVERTERS IN LASER BASED POWER SUPPLIES

Napajanje elektronskih naprav v ekstremnih in industrijskih okoljih pogosto zahteva uporabo visoko zanesljivih električnih napajalnikov, imunih na raznovrstne okolijske in elektromagnete motenje. Zahtevane specifikacije takšnih napajalnikov je mogoče doseči z uporabo sistemov, ki za izvor energije uporabljajo svetlobo laserskih virov. Energija v obliki monokromatske svetlobe je na oddaljeno mesto vodena skozi električno neprevodni medij, s čimer je dosežena inherentna neobčutljivost takšnih napajalnih sistemov na vse vrste elektromagnetih motenj. Lasersko svetlobo vodimo bodisi brezkontaktno po zraku ali priporočljivejše po električno neprevodnem optičnem vlaknu. V slednjem govorimo o sistemih za prenos »moči po optičnem vlaknu« (ang. Power–over–Fiber systems, PoF). Monokromatsko svetlobo je za napajanje elektronskih naprav potrebno pretvoriti v enosmerno električno energijo, kar storimo s fotonapetostnimi pretvorniki optimiziranimi za pretvorbo monokromatske svetlobe laserskih virov – »pretvorniki laserske moči« (ang. Laser Power Converter, LPC). PoF sistem je zaključen s priključitvijo podpornega elektronskega vezja na izhod pretvornika laserske moči, ki poskrbi za prilagoditev napetostnega nivoja za zanesljivo napajanje elektronskih naprav. PoF sistemi napajanja elektronskih naprav so našli svoje mesto v ekstremnih in industrijskih okoljih zaradi lastnosti kot so: • imunost na elektromagnetne motnje (enosmerna in izmenična električna in magnetna polja, razelektritve ozračja, radiofrekvenčne motnje, …), • velika prebojna trdnost med izvorom energije in napajano napravo, • majhna teža vodnikov energije (optična vlakna), • pri poškodbi vodnikov energije ne prihaja do iskrenja, … Zaradi omenjenih lastnosti so bili PoF sistemi razviti in uporabljeni za napajanje: • senzorjev za merjenje parametrov visokonapetostnih daljnovodov, • elektronskih merilnikov pod vodno gladino, • elektronskih podsklopov naprav za magnetno resonanco, • brezpilotnih letal, • elektronskih implantatov v človeškem telesu, • kontrolnih podsistemov v satelitih, • nadzornih video kamer, • merilnikov obratovalnih parametrov vetrnih turbin, … Kljub uspešni implementaciji PoF sistemov v nekaterih nišnih aplikacijah, je prenos energije z lasersko svetlobo še vedno razmeroma neznana tehnološka rešitev. Razlogov za to je veliko, verjetno pa je eden glavnih nizek izkoristek takšnega prenosa energije, ki se v praksi na sistemski ravni giblje nekje med 10 % in 30 %. Največ vložene energije se izgubi pri pretvorbi elektrike v svetlobo, pri čemer sodobne laserske diode dosegajo izkoristke med 40 % in 70 % ter nadalje pri pretvorbi laserske svetlobe nazaj v elektriko, pri čemer najboljši pretvorniki laserske moči dosegajo učinkovitost pretvorbe med 40 % in 60 %. V večini praktičnih aplikacij izgube pri prvotni pretvorbi energije iz elektrike v svetlobo s sistemskega vidika niso problematične, saj je laser postavljen na mestu, kjer je zagotovljena oskrba s potrebno električno energijo. Večje omejitve predstavljajo približno polovične izgube energije pri pretvorbi laserske svetlobe v električno energijo, preostanek energije pa je še dodatno zmanjšan za 10 % do 20 % zaradi izgub na podporni elektroniki. Tako v praksi izgube na sprejemni strani omejujejo največjo električno moč, ki jo lahko napajani napravi zanesljivo zagotovi en pretvornik laserske moči, na približno 1 W. Takšna omejitev največje dovedene moči ne predstavlja večjih problemov za napajanje nizkoenergijskih senzorjev, vendar omejuje doseg splošne uporabnosti PoF sistemov. V želji po razširitvi uporabnosti PoF sistemov se pričajoča doktorska naloga osredotoča na odkrivanje glavnih izgubnih mehanizmov v pretvornikih laserske moči in podporne elektronike. Rezultati sistematične analize in kvantitativnega ovrednotenja izgub so pripeljali do konceptualnih predlogov za izboljšanje sedanjih pretvornikov laserske moči.Electronic devices in extreme and industrial environments often require specialized power supplies immune to a variety of environmental and electromagnetic interferences. Such requirements can be met with power supplies that use lasers as an energy source. The laser light can be transmitted to a powered electronic device either wirelessly through the air or preferably through electrically nonconductive optical fiber. In the latter case, such power supplies are commonly known as Power–over–Fiber (PoF) systems. Energy in the form of monochromatic light must be transformed into electrical energy to power electronic devices. This energy transformation is achieved with photovoltaic (PV) devices optimized for conversion of monochromatic laser light called Laser Power Converters (LPC). Theoretically possible light-to-electricity conversion efficiency of LPCs is impaired by a variety of optical and electrical losses and light energy that is not converted into electrical energy results in energy loss, which in return reduces PoF systems efficiency. For high system efficiencies, LPCs must be made out of an appropriately selected high-quality III-V semiconductors and currently, the best manufactured LPCs exceed 60% conversion efficiency at strictly controlled laboratory conditions. Even thou such a figure is unheard of for the solar cells, an optimized PV converter illuminated with monochromatic light can theoretically convert more than 75% of impinged light to electricity, under the same conditions as the stated manufactured LPC. In this thesis, the reason for such a discrepancy between theoretical and practical conversion efficiency is studied in details and further, novel supporting electronics for LPCs in PoF systems are devised and analyzed in order to increase the system efficiency

Blood-coated sensor for high-throughput ptychographic cytometry on a Blu-ray disc

Blu-ray drive is an engineering masterpiece that integrates disc rotation, pickup head translation, and three lasers in a compact and portable format. Here we integrate a blood-coated image sensor with a modified Blu-ray drive for high-throughput cytometric analysis of various bio-specimens. In this device, samples are mounted on the rotating Blu-ray disc and illuminated by the built-in lasers from the pickup head. The resulting coherent diffraction patterns are then recorded by the blood-coated image sensor. The rich spatial features of the blood-cell monolayer help down-modulate the object information for sensor detection, thus forming a high-resolution computational bio-lens with a theoretically unlimited field of view. With the acquired data, we develop a lensless coherent diffraction imaging modality termed rotational ptychography for image reconstruction. We show that our device can resolve the 435 nm linewidth on the resolution target and has a field of view only limited by the size of the Blu-ray disc. To demonstrate its applications, we perform high-throughput urinalysis by locating disease-related calcium oxalate crystals over the entire microscope slide. We also quantify different types of cells on a blood smear with an acquisition speed of ~10,000 cells per second. For in vitro experiment, we monitor live bacterial cultures over the entire Petri dish with single-cell resolution. Using biological cells as a computational lens could enable new intriguing imaging devices for point-of-care diagnostics. Modifying a Blu-ray drive with the blood-coated sensor further allows the spread of high-throughput optical microscopy from well-equipped laboratories to citizen scientists worldwide

Doctor of Philosophy

dissertationDiffractive optics, an important part of modern optics, involves the control of optical fields by thin microstructured elements via diffraction and interference. Although the basic theoretical understanding of diffractive optics has been known for a long time, many of its applications have not yet been explored. As a result, the field of diffractive optics is old and young at the same time. The interest in diffractive optics originates from the fact that diffractive optical elements are flat and lightweight. This makes their applications into compact optical systems more feasible compared to bulky refractive optics. Although these elements demonstrate excellent diffraction efficiency for monochromatic light, they fail to generate complex intensity profiles under broadband illumination. This is due to the fact that the degrees-of-freedom in these elements are insufficient to overcome their strong chromatic aberration. As a result, despite their so many advantages over refractive optics, their applications are somewhat limited in broadband systems. In this dissertation, a recently developed diffractive optical element, called a polychromat, is demonstrated for several broadband applications. The polychromat is comprised of linear "grooves" or square "pixels" with feature size in the micrometer scale. The grooves or pixels can have multiple height levels. Such grooved or pixelated structures with multilevel topography provide enormous degrees-of-freedom which in turn facilitates generation of complex intensity distributions with high diffraction efficiency under broadband illumination. Furthermore, the super-wavelength feature size and low aspect ratio of this micro-optic make its fabrication process simpler. Also, this diffractive element is not polarization sensitive. As a result, the polychromat holds the potential to be used in numerous technological applications. Throughout this dissertation, the broadband operation of the polychromat is demonstrated in four different areas, namely, photovoltaics, displays, lenses and holograms. Specifically, we have developed a polychromat-photovoltaic system which facilitates better photon-to-electron conversion via spectrum splitting and concentration, a modified liquid crystal display (LCD) that offers higher luminance compared to a standard LCD, a cylindrical lens that demonstrates super-achromatic focusing over the entire visible band, a planar diffractive lens that images over the visible and near-IR spectrum and broadband transmission holograms that project complex full-color images with high efficiency. In each of these applications, a unique figure of merit was defined and the height topography of the polychromat was optimized to maximize the figure of merit. The optimization was achieved with the aid of scalar diffraction theory and a modified version of direct binary search algorithm. Single step grayscale lithography was developed and optimized to fabricate these devices with the smallest possible fabrication errors. Rigorous characterization of these systems demonstrated broadband performance of the polychromat in all of the applications

Instrument design and optimization of interferometric reflectance imaging sensors for in vitro diagnostics

Thesis (Ph.D.)--Boston UniversityIn the field of drug discovery and disease diagnostics, protein microarrays have generated much enthusiasm for their high-throughput monitoring of biomarkers; however, this technology has yet to translate from research laboratories to commercialization. The hindrance is the considerable uncertainty and skepticism regarding data obtained. The disparity in results from different laboratories performing identical tests is attributed to a lack of assay quality control. Unlike DNA microarrays, protein microarrays have a higher level of bioreceptor immobilization variability and non-specific binding because of the more complex molecular structure and broader physiochemical properties. Traditional assay detection modalities, such as fluorescence microscopy and surface plasmon resonance, are unable to overcome both of these sources of variation. This dissertation describes the hardware and software design and biological validation of three complementary platforms that overcome bioreceptor variability and non-specific binding for diagnostics. In order to quantify the bioreceptor quality, a label-free, nondestructive, low cost, and high-throughput interferometric sensor has been developed as a quality control tool. The quality control tool was combined with a wide-field fluorescence imaging system to improve fluorescence experimental repeatability. Lastly, a novel high-throughput and label-free platform for quality control and specific protein microarray detection is described. This platform overcomes the additional complexities and time required with labeled assays by discriminating between specific and nonspecific detection by including sizing of individual binding events. Protein microarrays may one day emerge as routine clinical laboratory tests; however, it is important that the proper quality control procedures are in place to minimize erroneous results. These platforms provide reliable and repeatable protein microarray measurements for new advancements in disease diagnostics with the potential for drug discovery

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions