Compact infrared pinhole fisheye for wide field applications

International audienceThe performances of a compact infrared optical system using advanced pinhole optics for wide field applications are given. This concept is adapted from the classical Tisse design in order to fit with infrared issues. Despite a low light gathering efficiency and a low resolution in comparison with classical lenses, pinhole imagery provides a long depth of field and a wide angular field of view. Moreover, by using a simple lens that compresses the field of view, the angular acceptance of this pinhole camera can be drastically widened to a value around 180{\textdegree}. This infrared compact system is named pinhole fisheye since it is based on the field lens of a classical fisheye system

Beyond solid-state lighting: Miniaturization, hybrid integration, and applications og GaN nano- and micro-LEDs

Gallium Nitride (GaN) light-emitting-diode (LED) technology has been the revolution in modern lighting. In the last decade, a huge global market of efficient, long-lasting and ubiquitous white light sources has developed around the inception of the Nobel-price-winning blue GaN LEDs. Today GaN optoelectronics is developing beyond lighting, leading to new and innovative devices, e.g. for micro-displays, being the core technology for future augmented reality and visualization, as well as point light sources for optical excitation in communications, imaging, and sensing. This explosion of applications is driven by two main directions: the ability to produce very small GaN LEDs (microLEDs and nanoLEDs) with high efficiency and across large areas, in combination with the possibility to merge optoelectronic-grade GaN microLEDs with silicon microelectronics in a fully hybrid approach. GaN LED technology today is even spreading into the realm of display technology, which has been occupied by organic LED (OLED) and liquid crystal display (LCD) for decades. In this review, the technological transition towards GaN micro- and nanodevices beyond lighting is discussed including an up-to-date overview on the state of the art

A Novel Vertebrate Eye Using Both Refractive and Reflective Optics

SummarySunlight is attenuated rapidly in the ocean, resulting in little visually useful light reaching deeper than ∼1000 m in even the clearest water [1]. To maximize sensitivity to the relatively brighter downwelling sunlight, to view the silhouette of animals above them, and to increase the binocular overlap of their eyes, many mesopelagic animals have developed upward-pointing tubular eyes [2–4]. However, these sacrifice the ability to detect bioluminescent [5] and reflective objects in other directions. Thus, some mesopelagic fish with tubular eyes extend their visual fields laterally and/or ventrally by lensless ocular diverticula, which are thought to provide unfocused images, allowing only simple detection of objects, with little spatial resolution [2–4]. Here, we show that a medial mirror within the ventrally facing ocular diverticulum of the spookfish, Dolichopteryx longipes, consisting of a multilayer stack derived from a retinal tapetum, is used to reflect light onto a lateral retina. The reflective plates are not orientated parallel to the surface of the mirror. Instead, plate angles change progressively around the mirror, and computer modeling indicates that this provides a well-focused image. This is the first report of an ocular image being formed in a vertebrate eye by a mirror

Charting Evolution’s Trajectory: Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution

For over 100 years, molluscan eyes have been used as an example of convergent evolution and, more recently, as a textbook example of stepwise evolution of a complex lens eye via natural selection. Yet, little is known about the underlying mechanisms that create the eye and generate different morphologies. Assessing molluscan eye diversity and understanding how this diversity came about will be important to developing meaningful interpretations of evolutionary processes. This paper provides an introduction to the myriad of eye types found in molluscs, focusing on some of the more unusual structures. We discuss how molluscan eyes can be applied to the study of evolution by examining patterns of convergent and parallel evolution and provide several examples, including the putative convergence of the camera-type eyes of cephalopods and vertebrates

An Optofluidic Lens Biochip and an x-ray Readable Blood Pressure Microsensor: Versatile Tools for in vitro and in vivo Diagnostics.

Three different microfabricated devices were presented for use in vivo and in vitro diagnostic biomedical applications: an optofluidic-lens biochip, a hand held digital imaging system and an x-ray readable blood pressure sensor for monitoring restenosis. An optofluidic biochip–termed the ‘Microfluidic-based Oil-Immersion Lens’ (mOIL) biochip were designed, fabricated and test for high-resolution imaging of various biological samples. The biochip consists of an array of high refractive index (n = 1.77) sapphire ball lenses sitting on top of an oil-filled microfluidic network of microchambers. The combination of the high optical quality lenses with the immersion oil results in a numerical aperture (NA) of 1.2 which is comparable to the high NA of oil immersion microscope objectives. The biochip can be used as an add-on-module to a stereoscope to improve the resolution from 10 microns down to 0.7 microns. It also has a scalable field of view (FOV) as the total FOV increases linearly with the number of lenses in the biochip (each lens has ~200 microns FOV). By combining the mOIL biochip with a CMOS sensor, a LED light source in 3D printed housing, a compact (40 grams, 4cmx4cmx4cm) high resolution (~0.4 microns) hand held imaging system was developed. The applicability of this system was demonstrated by counting red and white blood cells and imaging fluorescently labelled cells. In blood smear samples, blood cells, sickle cells, and malaria-infected cells were easily identified. To monitor restenosis, an x-ray readable implantable blood pressure sensor was developed. The sensor is based on the use of an x-ray absorbing liquid contained in a microchamber. The microchamber has a flexible membrane that is exposed to blood pressure. When the membrane deflects, the liquid moves into the microfluidic-gauge. The length of the microfluidic-gauge can be measured and consequently the applied pressure exerted on the diaphragm can be calculated. The prototype sensor has dimensions of 1x0.6x10mm and adequate resolution (19mmHg) to detect restenosis in coronary artery stents from a standard chest x-ray. Further improvements of our prototype will open up the possibility of measuring pressure drop in a coronary artery stent in a non-invasively manner.PhDMacromolecular Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111384/1/toning_1.pd

Development of Molecular Contrast-enhanced Imaging for Optical Coherence Tomography

Biological imaging techniques that are able to detect a contrast-enhanced signal from the target molecules have been widely applied to various techniques in the imaging field. The complex biological environment provides numerous and more efficient pathways along which the chromophores (light absorber) may release its energy. This energy can provide not only morphological information, but also specific molecular information such as a biochemical map of a sample. All diseases correlate with both morphological and biochemical changes. Optical coherence tomography (OCT) system is one of the biological imaging techniques. OCT has widely been applied to many medical/clinical fields, giving benefit from a penetration depth of a few millimeters while maintaining a spatial resolution on the order of a micron. Unfortunately, OCT lacks the straightforward functional molecular imaging extensions available for other technologies, e.g. confocal fluorescence microscopy and fluorescence diffuse optical tomography. This is largely because incoherent processes such as fluorescence emission and Raman scattering are not readily detectable with low coherence interferometry that is the central technique that underlies all OCT systems. Despite a drawback of molecular imaging with OCT, it is highly desirable to measure not only morphological, but also molecular information from either endogenous or exogenous molecules. In order to overcome the limitation of molecular contrast imaging for OCT, our group has been researched the hybrid OCT imaging technique and a new exogenous contrast agent. Our contrast-enhanced imaging technique integrates OCT with a well-researched and well-established technique: two-colored pump-probe absorption spectroscopy. Our novel imaging technique is called Pump-Probe OCT (PPOCT). Based upon current successful results, molecular imaging with OCT potentially gives us the ability to identify pathologies. In order to expand the capacity of PPOCT, this dissertation focuses on development of molecular contrast-enhanced imaging for optical coherence tomography (OCT). In the first phase of the research, we developed and optimized for sensitivity a two-color ground state recovery Pump-Probe Optical Coherence Tomography (gsrPPOCT) system and signal algorithm to measure the contrast-enhanced signal of endogenous and exogenous contrast agents such as Hemoglobin (Hb) and Methylene blue (MB) from in vivo samples. Depending on the absorption peak of a target molecule, the pump light sources for PPOCT used 532nm Q-switched laser or 663nm diode laser. Based on different experimental application, Ti:sapp or SLD of 830nm center wavelength were utilized. The PPCOT system was firstly used to image Hb of in vivo vasulature in a Xenopus laevis as the endogenous contrast agent and a larval stage zebrafish using MB as the exogenous contrast agent via transient changes in light absorption. Their morphological in addition to molecular specific information from a live animal was described. The incorporation of a pump laser in an otherwise typical spectrometer based OCT system is sufficient to enable molecular imaging with PPOCT. In the second phase of this research, based on endoscopic molecular contrast-enhanced applications for OCT, we invented an ultra-wideband lensless fiber optic rotary joint based on co-aligning two optical fibers has excellent performance (~0.38 dB insertion loss). The developed rotary joint can cover a wavelength range of at least 355- 1360 nm with single mode, multimode, and double clad fibers with rotational velocities up to 8800 rpm (146 Hz). In the third phase of this research, we developed and manufactured a microencapsulated methylene blue (MB) contrast agent for PPOCT. The poly lactic coglycolic acid (PLGA) microspheres loaded with MB offer several advantages over bare MB. The microsphere encapsulation improves the PPOCT signal both by enhancing the scattering and preventing the reduction of MB to leucomethylene blue. The surface of the microsphere can readily be functionalized to enable active targeting of the contrast agent without modifying the excited state dynamics of MB that enable PPOCT imaging. Both MB and PLGA are used clinically. PLGA is FDA approved and used in drug delivery and tissue engineering applications. 2.5 µm diameter microspheres were synthesized with an inner core containing 0.01% (w/v) aqueous MB. As an initial demonstration the MB microspheres were imaged in a 100 µm diameter capillary tube submerged in a 1% intralipid emulsion. By varying the oxygen concentration both 0% and 21%, we observed he lifetime of excited triple state using time-resolved Pump-Probe spectroscopy and also the relative phase shift between the pump and probe is a reliable indicator of the oxygen concentration. Furthermore, these results are in good agreement with our theoretical predictions. This development opens up the possibility of using MB for 3-D oxygen sensing with PPOCT

Development of Molecular Contrast-enhanced Imaging for Optical Coherence Tomography

Biological imaging techniques that are able to detect a contrast-enhanced signal from the target molecules have been widely applied to various techniques in the imaging field. The complex biological environment provides numerous and more efficient pathways along which the chromophores (light absorber) may release its energy. This energy can provide not only morphological information, but also specific molecular information such as a biochemical map of a sample. All diseases correlate with both morphological and biochemical changes. Optical coherence tomography (OCT) system is one of the biological imaging techniques. OCT has widely been applied to many medical/clinical fields, giving benefit from a penetration depth of a few millimeters while maintaining a spatial resolution on the order of a micron. Unfortunately, OCT lacks the straightforward functional molecular imaging extensions available for other technologies, e.g. confocal fluorescence microscopy and fluorescence diffuse optical tomography. This is largely because incoherent processes such as fluorescence emission and Raman scattering are not readily detectable with low coherence interferometry that is the central technique that underlies all OCT systems. Despite a drawback of molecular imaging with OCT, it is highly desirable to measure not only morphological, but also molecular information from either endogenous or exogenous molecules. In order to overcome the limitation of molecular contrast imaging for OCT, our group has been researched the hybrid OCT imaging technique and a new exogenous contrast agent. Our contrast-enhanced imaging technique integrates OCT with a well-researched and well-established technique: two-colored pump-probe absorption spectroscopy. Our novel imaging technique is called Pump-Probe OCT (PPOCT). Based upon current successful results, molecular imaging with OCT potentially gives us the ability to identify pathologies. In order to expand the capacity of PPOCT, this dissertation focuses on development of molecular contrast-enhanced imaging for optical coherence tomography (OCT). In the first phase of the research, we developed and optimized for sensitivity a two-color ground state recovery Pump-Probe Optical Coherence Tomography (gsrPPOCT) system and signal algorithm to measure the contrast-enhanced signal of endogenous and exogenous contrast agents such as Hemoglobin (Hb) and Methylene blue (MB) from in vivo samples. Depending on the absorption peak of a target molecule, the pump light sources for PPOCT used 532nm Q-switched laser or 663nm diode laser. Based on different experimental application, Ti:sapp or SLD of 830nm center wavelength were utilized. The PPCOT system was firstly used to image Hb of in vivo vasulature in a Xenopus laevis as the endogenous contrast agent and a larval stage zebrafish using MB as the exogenous contrast agent via transient changes in light absorption. Their morphological in addition to molecular specific information from a live animal was described. The incorporation of a pump laser in an otherwise typical spectrometer based OCT system is sufficient to enable molecular imaging with PPOCT. In the second phase of this research, based on endoscopic molecular contrast-enhanced applications for OCT, we invented an ultra-wideband lensless fiber optic rotary joint based on co-aligning two optical fibers has excellent performance (~0.38 dB insertion loss). The developed rotary joint can cover a wavelength range of at least 355- 1360 nm with single mode, multimode, and double clad fibers with rotational velocities up to 8800 rpm (146 Hz). In the third phase of this research, we developed and manufactured a microencapsulated methylene blue (MB) contrast agent for PPOCT. The poly lactic coglycolic acid (PLGA) microspheres loaded with MB offer several advantages over bare MB. The microsphere encapsulation improves the PPOCT signal both by enhancing the scattering and preventing the reduction of MB to leucomethylene blue. The surface of the microsphere can readily be functionalized to enable active targeting of the contrast agent without modifying the excited state dynamics of MB that enable PPOCT imaging. Both MB and PLGA are used clinically. PLGA is FDA approved and used in drug delivery and tissue engineering applications. 2.5 µm diameter microspheres were synthesized with an inner core containing 0.01% (w/v) aqueous MB. As an initial demonstration the MB microspheres were imaged in a 100 µm diameter capillary tube submerged in a 1% intralipid emulsion. By varying the oxygen concentration both 0% and 21%, we observed he lifetime of excited triple state using time-resolved Pump-Probe spectroscopy and also the relative phase shift between the pump and probe is a reliable indicator of the oxygen concentration. Furthermore, these results are in good agreement with our theoretical predictions. This development opens up the possibility of using MB for 3-D oxygen sensing with PPOCT

MICROSCOPE IN DENTISTRY: A REVIEW ARTICLE

The microscope has been one of the oldest yet most exquisite inventions in human history. The lenses changed the future of medical science and its abstraction forever. Previously, humans never know much about the source of disease, but today we know that the universe of microbes is vaster and more limitless than it ever was. However, the microscope is not just limited to laboratory in vitro research and study; it has remodeled dentistry more today than ever. This article describes the various types of microscopes used in periodontics, endodontics, and oral pathology in dentistry

Physics vs. Learned Priors: Rethinking Camera and Algorithm Design for Task-Specific Imaging

Cameras were originally designed using physics-based heuristics to capture aesthetic images. In recent years, there has been a transformation in camera design from being purely physics-driven to increasingly data-driven and task-specific. In this paper, we present a framework to understand the building blocks of this nascent field of end-to-end design of camera hardware and algorithms. As part of this framework, we show how methods that exploit both physics and data have become prevalent in imaging and computer vision, underscoring a key trend that will continue to dominate the future of task-specific camera design. Finally, we share current barriers to progress in end-to-end design, and hypothesize how these barriers can be overcome

Robust deep learning for computational imaging through random optics

Light scattering is a pervasive phenomenon that poses outstanding challenges in both coherent and incoherent imaging systems. The output of a coherent light scattered from a complex medium exhibits a seemingly random speckle pattern that scrambles the useful information of the object. To date, there is no simple solution for inverting such complex scattering. Advancing the solution of inverse scattering problems could provide important insights into applications across many areas, such as deep tissue imaging, non-line-of-sight imaging, and imaging in degraded environment. On the other hand, in incoherent systems, the randomness of scattering medium could be exploited to build lightweight, compact, and low-cost lensless imaging systems that are applicable in miniaturized biomedical and scientific imaging. The imaging capabilities of such computational imaging systems, however, are largely limited by the ill-posed or ill-conditioned inverse problems, which typically causes imaging artifacts and degradation of the image resolution. Therefore, mitigating this issue by developing modern algorithms is essential for pushing the limits of such lensless computational imaging systems. In this thesis, I focus on the problem of imaging through random optics and present two novel deep-learning (DL) based methodologies to overcome the challenges in coherent and incoherent systems: 1) no simple solution for inverse scattering problem and lack of robustness to scattering variations; and 2) ill-posed problem for diffuser-based lensless imaging. In the first part, I demonstrate the novel use of a deep neural network (DNN) to solve the inverse scattering problem in a coherent imaging system. I propose a `one-to-all' deep learning technique that encapsulates a wide range of statistical variations for the model to be resilient to speckle decorrelations. I show for the first time, to the best of my knowledge, that the trained CNN is able to generalize and make high-quality object prediction through an entirely different set of diffusers of the same macroscopic parameter. I then push the limit of robustness against a broader class of perturbations including scatterer change, displacements, and system defocus up to 10X depth of field. In the second part, I consider the utility of the random light scattering to build a diffuser-based computational lensless imaging system and present a generally applicable novel DL framework to achieve fast and noise-robust color image reconstruction. I developed a diffuser-based computational funduscope that reconstructs important clinical features of a model eye. Experimentally, I demonstrated fundus image reconstruction over a large field of view (FOV) and robustness to refractive error using a constant point-spread-function. Next, I present a physics simulator-trained, adaptive DL framework to achieve fast and noise-robust color imaging. The physics simulator incorporates optical system modeling, the simulation of mixed Poisson-Gaussian noise, and color filter array induced artifacts in color sensors. The learning framework includes an adaptive multi-channel L2-regularized inversion module and a channel-attention enhancement network module. Both simulation and experiments show consistently better reconstruction accuracy and robustness to various noise levels under different light conditions compared with traditional L2-regularized reconstructions. Overall, this thesis investigated two major classes of problems in imaging through random optics. In the first part of the thesis, my work explored a novel DL-based approach for solving the inverse scattering problem and paves the way to a scalable and robust deep learning approach to imaging through scattering media. In the second part of the thesis, my work developed a broadly applicable adaptive learning-based framework for ill-conditioned image reconstruction and a physics-based simulation model for computational color imaging