Optimization of the holographic process for imaging and lithography

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 272-297).Since their invention in 1948 by Dennis Gabor, holograms have demonstrated to be important components of a variety of optical systems and their implementation in new fields and methods is expected to continue growing. Their ability to encode 3D optical fields on a 2D plane opened the possibility of novel applications for imaging and lithography. In the traditional form, holograms are produced by the interference of a reference and object waves recording the phase and amplitude of the complex field. The holographic process has been extended to include different recording materials and methods. The increasing demand for holographic-based systems is followed by a need for efficient optimization tools designed for maximizing the performance of the optical system. In this thesis, a variety of multi-domain optimization tools designed to improve the performance of holographic optical systems are proposed. These tools are designed to be robust, computationally efficient and sufficiently general to be applied when designing various holographic systems. All the major forms of holographic elements are studied: computer generated holograms, thin and thick conventional holograms, numerically simulated holograms and digital holograms. Novel holographic optical systems for imaging and lithography are proposed. In the case of lithography, a high-resolution system based on Fresnel domain computer generated holograms (CGHs) is presented. The holograms are numerically designed using a reduced complexity hybrid optimization algorithm (HOA) based on genetic algorithms (GAs) and the modified error reduction (MER) method. The algorithm is efficiently implemented on a graphic processing unit. Simulations as well as experimental results for CGHs fabricated using electron-beam lithography are presented. A method for extending the system's depth of focus is proposed. The HOA is extended for the design and optimization of multispectral CGHs applied for high efficiency solar concentration and spectral splitting. A second lithographic system based on optically recorded total internal reflection (TIR) holograms is studied. A comparative analysis between scalar and (cont.) vector diffraction theories for the modeling and simulation of the system is performed.A complete numerical model of the system is conducted including the photoresist response and first order models for shrinkage of the holographic emulsion. A novel block-stitching algorithm is introduced for the calculation of large diffraction patterns that allows overcoming current computational limitations of memory and processing time. The numerical model is implemented for optimizing the system's performance as well as redesigning the mask to account for potential fabrication errors. The simulation results are compared to experimentally measured data. In the case of imaging, a segmented aperture thin imager based on holographically corrected gradient index lenses (GRIN) is proposed. The compound system is constrained to a maximum thickness of 5mm and utilizes an optically recorded hologram for correcting high-order optical aberrations of the GRIN lens array. The imager is analyzed using system and information theories. A multi-domain optimization approach is implemented based on GAs for maximizing the system's channel capacity and hence improving the information extraction or encoding process. A decoding or reconstruction strategy is implemented using the superresolution algorithm. Experimental results for the optimization of the hologram's recording process and the tomographic measurement of the system's space-variant point spread function are presented. A second imaging system for the measurement of complex fluid flows by tracking micron sized particles using digital holography is studied. A stochastic theoretical model based on a stability metric similar to the channel capacity for a Gaussian channel is presented and used to optimize the system. The theoretical model is first derived for the extreme case of point source particles using Rayleigh scattering and scalar diffraction theory formulations. The model is then extended to account for particles of variable sizes using Mie theory for the scattering of homogeneous dielectric spherical particles. The influence and statistics of the particle density dependent cross-talk noise are studied. Simulation and experimental results for finding the optimum particle density based on the stability metric are presented. For all the studied systems, a sensitivity analysis is performed to predict and assist in the correction of potential fabrication or calibration errors.by José Antonio Domínguez-Caballero.Ph.D

Highly Efficient and Data Compressed Ultrafast Single-Pixel Imaging based on Photonic Time-Stretch

The research presented in this thesis is focused on highly efficient and data compressed ultrafast single pixel imaging (SPI) systems based on photonic time stretch (PTS) technique. Three ultrafast SPI systems are presented and analysed with unique features of low-cost, compact, highly efficient and optical data compression. The first ultrafast SPI system is a highly efficient, fibre-compatible ultrafast imaging system based on PTS using a 45° tilted fibre grating (45° TFG). The 45° TFG serves as an in-fibre lateral diffraction element, replacing bulky and lossy free- space diffraction gratings in conventional PTS imaging systems. This new design significantly reduces the volume of conventional PTS imaging systems, improves energy efficiency and system stability. A proof-of-principle demonstration of our proposed PTS imaging system is performed for the first time with improved spatial resolution and ultrafast detecting speed of 46 m/s. Secondly, data compressed ultrafast photonic time stretch imaging is investigated with the help of a spatial mask for spatial domain compressed sensing. In practice, a spatial light modulator (SLM) is utilized as a passive optical random pattern modulator, namely, spatial mask, in spatial domain. This combines the benefit of compressed sensing (CS) and PTS techniques. And a high speed CS imaging system is obtained with a compression ratio of 55.6%. Besides, time-domain CS applied in ultrafast real-time optical coherent tomography (OCT) is experimentally demonstrated as well. Finally, an all-optical CS imaging system based on PTS and multimode interference using a multimode fibre (MMF) is demonstrated. The MMF acts as a low-cost random optical speckle pattern generator based on ultrafast wavelength tuning in PTS. Each wavelength of the optical light generates a repeatable and stable random optical speckle pattern, which has the feature of low- correlated relation between different optical speckle patterns. This technique can overcome the speed limit in existing CS photonic time stretch imaging, where imaging speed is much lower than the pulse repetition rate

Principle and recent development in photonic time-stretch imaging

Inspiring development in optical imaging enables great applications in the science and engineering industry, especially in the medical imaging area. Photonic time-stretch imaging is one emerging innovation that attracted a wide range of attention due to its principle of one-to-one-to-one mapping among space-wavelength-time using dispersive medium both in spatial and time domains. The ultrafast imaging speed of the photonics time-stretch imaging technique achieves an ultrahigh frame rate of tens of millions of frames per second, which exceeds the traditional imaging methods in several orders of magnitudes. Additionally, regarding ultrafast optical signal processing, it can combine several other optical technologies, such as compressive sensing, nonlinear processing, and deep learning. In this paper, we review the principle and recent development of photonic time-stretch imaging and discuss the future trends

Microoptical multi aperture imaging systems

Die Verkleinerung digitaler Einzelapertur-Abbildungssysteme erreicht aktuell physikalische sowie technische Limits. Die Miniaturisierung führt zu einer Verringerung sowohl des Auflösungsvermögens als auch des Signal-Rausch-Verhältnisses. Einen Ausweg zeigen die Prinzipien der kleinsten in der Natur bekannten Sehsysteme - die Facettenaugen. Die parallelisierte Anordnung einer großen Anzahl von Optiken ermöglicht, trotz der geringen Baugröße, eine große Informationsmenge aus einem ausgedehnten Gesichtsfeld zu übertragen. Ziel ist es, die Vorteile natürlicher Facettenaugen zu analysieren und diese zur Überwindung aktueller Grenzen der Miniaturisierung von digitalen Kameras zu adaptieren. Durch die Synergie von Optik, Opto-Elektronik und Bildverarbeitung wird die Miniaturisierung unter Erreichung praxisrelevanter Parameter angestrebt. Dafür wurde eine systematische Einteilung bereits bekannter und neuartiger Prinzipien von Multiapertur-Abbildungssystemen vorgenommen. Das grundlegende Verständnis der Vor- und Nachteile sowie des Skalierungsverhaltens der verschiedenen Ansätze ermöglichte die detaillierte Untersuchung der zwei erfolgversprechendsten Systemklassen. Für die Auslegung der Multiapertur-Optiken wurde eine Kombination aus Ansätzen des klassischen Optikdesigns und neuen semi-automatisierten Simulations- und Optimierungsmethoden mittels Ray-Tracing angewandt. Die mit natürlichen Facettenaugen vergleichbare Größe der Optiken ermöglichte die Verwendung mikrooptischer Herstellungsverfahren im Wafermaßstab. Es wurden Prototypen experimentell untersucht und die simulierten Systemparameter mit Hilfe der für die Multiapertur Anordnungen angepassten Messmethoden bestätigt. Die dargestellten Lösungen demonstrieren grundsätzlich neue Ansätze für den Bereich der hochauflösenden, miniaturisierten Abbildungsoptik, die kleinste Baulängen bei gegebenem Auflösungsvermögen erzielen. Somit sind sie im Stande die Skalierungslimits der Einzelapertur-Abbildungsoptik zu überwinden

Optics in Our Time

Optics, Lasers, Photonics, Optical Devices; Quantum Optics; Popular Science in Physics; History and Philosophical Foundations of Physic

Generation and characterization of spatially structured few-photon states of light

The present doctoral dissertation discusses the results of research on the characterization of spatial structure and statistical properties of few-photon states of light generated i.a. with the use of a new source based on multimode atomic memory. The dissertation comprises nine chapters grouped into the following parts: a literature and theoretical introduction, and three main parts providing the experimental results. Part I discusses the characteristics of a scientific complementary metal-oxide semiconductor camera equipped with an image intensifier (I-sCMOS) constructed by our group. We provide theoretical models of saturation of photon-number-resolving detectors which relate qualitatively to our camera. We perform experimental tomography of the I-sCMOS camera and use its results for high-fidelity reconstruction of the original statistics of the impinging light. In Part II we present an atomic memory setup in warm rubidium vapors where the write-in and readout occur due to collective Raman scattering. The memory is able to store information about the spatial structure of light. We describe the experimental setup thoroughly, with particular attention to the filtering system. We characterize multimode Raman scattering and investigate the storage performance of the memory which is limited by diffusional decoherence. We demonstrate spatial correlations between delayed Stokes and anti-Stokes photons. Using the I-sCMOS camera together with an advanced filtering system we observe spatial correlations down to single atomic excitations per memory mode. In Part III we discuss the use of the I-sCMOS camera to observe the Hong-Ou-Mandel two-photon interference with spatial resolution. We study the influence of finite spatial distinguishability of photons on the interference results, which leads us to measurements of the local spatial structure of a single photon. We observe and examine closely the following relatively unexplored phenomena. In Part I we investigate seemingly nonclassical effects in measurements of photon counts statistics on the camera. In Part II we are the first ones to show multimode Raman scattering in atomic memories. Finally, in Part III we describe the first observation of the Hong-Ou-Mandel effect with spatial resolution which is studied further in terms of finite spatial distinguishability of the interfering photons. In this thesis, we present the following novel experimental methodology. We use a new-type of I-sCMOS camera. We implement and perform the reconstruction of photon statistics based on tomographic characterization of the detector. We also build an efficient filtering system for photons generated in atomic memory. Moreover, we create an accurate method of measuring diffusion coefficients in atomic memory. We present our own methods of spatial characterization of the properties of light. Eventually, we introduce an entirely novel method: holographic measurement of the phase structure of a single photon using i.a. a specially developed phase reconstruction algorithm. The presented results fall within the scope of contemporary research in quantum optics and have a number of possible applications, as discussed in the final remarks section.Niniejsza praca doktorska prezentuje wyniki badań poświęconych charakteryzacji struktury przestrzennej i właściwości statystyk kilkufotonowych stanów światła generowanych m.in. z użyciem nowego źródła opartego na wielomodowej pamięci atomowej. Praca składająca się z 9 rozdziałów podzielona jest na wstęp literaturowy i teoretyczny oraz trzy części zawierające merytoryczne wyniki badań. Kolejno w części I prezentujemy i charakteryzujemy skonstruowany układ kamery sCMOS ze wzmacniaczem obrazu (I-sCMOS). Przedstawiamy teoretyczne modele nasycania detektorów rozróżniających liczbę fotonów, które jakościowo odnoszą się do kamery. Przeprowadzamy eksperymentalną tomografię kamery I-sCMOS a jej wyniki wykorzystujemy do wiernej rekonstrukcji pierwotnych statystyk światła padającego na kamerę. W części II prezentujemy układ pamięci atomowej w ciepłych parach rubidu, do której zapis i odczyt odbywa się w wyniku kolektywnego rozpraszania Ramana. Pamięć jest w stanie przechować informacje na temat przestrzennej struktury światła. Dokładnie opisujemy układ doświadczalny, w szczególności pod kątem układu filtrowania. Charakteryzujemy wielomodowe rozpraszanie Ramana oraz badamy zdolność przechowywania pamięci ograniczoną dekoherencją dyfuzyjną. Demonstrujemy korelacje przestrzenne pomiędzy opóźnionymi w czasie fotonami Stokesa i anty-Stokesa. Używając kamery I-sCMOS i zaawansowanego systemu filtrowania obserwujemy korelacje przestrzenne aż do reżimu pojedynczych wzbudzeń atomowych na mod pamięci. W części III wykorzystujemy kamerę I-sCMOS do badania zjawiska interferencji dwufotonowej Hong-Ou-Mandela obserwowanego z rozdzielczością przestrzenną. Studiujemy wpływ skończonej widzialności przestrzennej na wynik interferencji, która służy nam do pomiaru lokalnej struktury przestrzennej pojedynczego fotonu. Zaobserwowaliśmy i zbadaliśmy następujące słabo zbadane zjawiska. W części I badamy pozorne efekty nieklasyczne w statystykach zliczeń fotonów zmierzonych za pomocą kamery. W części II po raz pierwszy pokazujemy wielomodowe rozpraszanie Ramana w pamięciach atomowych. Natomiast w części III prezentujemy pierwszą obserwację efektu Hong-Ou-Mandela z rozdzielczością przestrzenną, którą następnie badamy pod kątem wpływu skończonej rozróżnialności przestrzennej interferujących fotonów. Na potrzeby tej pracy zostały stworzone i opracowane następujące, nowe metodologie badawcze. Stosujemy nowego typu kamerę I-sCMOS, opracowujemy rekonstrukcje statystyk fotonów na podstawie tomograficznej charakteryzacji detektora. Konstruujemy skuteczny układ filtrowania fotonów w pamięci atomowej. Tworzymy nową dokładną metodę pomiaru współczynników dyfuzji w pamięci atomowej. Prezentujemy także własne metody charakteryzacji przestrzennej statystycznych właściwości światła. W końcu, pokazujemy zupełnie nowatorską metodę holograficznego pomiaru struktury fazy pojedynczego fotonu, wykorzystującą m.in. specjalnie stworzony algorytm rekonstrukcji fazy. Zaprezentowane wyniki wpisują się w kontekst współczesnych badań w optyce kwantowej, a także posiadają szereg potencjalnych zastosowań, przedyskutowanych w podsumowaniu pracy

Towards Better Methods of Stereoscopic 3D Media Adjustment and Stylization

Stereoscopic 3D (S3D) media is pervasive in film, photography and art. However, working with S3D media poses a number of interesting challenges arising from capture and editing. In this thesis we address several of these challenges. In particular, we address disparity adjustment and present a layer-based method that can reduce disparity without distorting the scene. Our method was successfully used to repair several images for the 2014 documentary “Soldiers’ Stories” directed by Jonathan Kitzen. We then explore consistent and comfortable methods for stylizing stereo images. Our approach uses a modified version of the layer-based technique used for disparity adjustment and can be used with a variety of stylization filters, including those in Adobe Photoshop. We also present a disparity-aware painterly rendering algorithm. A user study concluded that our layer-based stylization method produced S3D images that were more comfortable than previous methods. Finally, we address S3D line drawing from S3D photographs. Line drawing is a common art style that our layer-based method is not able to reproduce. To improve the depth perception of our line drawings we optionally add stylized shading. An expert survey concluded that our results were comfortable and reproduced a sense of depth

Anamorphic pixels for multi-channel superresolution

Superresolution from plenoptic cameras or camera arrays is usually treated similarly to superresolution from video streams. However, the transformation between the low-resolution views can be determined precisely from camera geometry and parallax. Furthermore, as each low-resolution image originates from a unique physical camera, its sampling properties can also be unique. We exploit this option with a custom design of either the optics or the sensor pixels. This design makes sure that the sampling matrix of the complete system is always well-formed, enabling robust and high-resolution image reconstruction. We show that simply changing the pixel aspect ratio from square to anamorphic is sufficient to achieve that goal, as long as each camera has a unique aspect ratio. We support this claim with theoretical analysis and image reconstruction of real images. We derive the optimal aspect ratios for sets of 2 or 4 cameras. Finally, we verify our solution with a camera system using an anamorphic lens