176,392 research outputs found
Towards Large Scale CMOS Single-Photon Detector Arrays for Lab-on-Chip Applications
Single-photon detection is useful in many domains requiring time-resolved imaging, high sensitivity and high dynamic range. In this paper the miniaturization and performance potential of solid-state single-photon detectors are discussed in the context of lab-on-chip applications where high accuracy and/or high levels of parallelism are suited. Technological and design trade-offs are discussed in view of recent advances in integrated LED matrix technology and the emergence of new multiplication based architectures
Micro Fourier Transform Profilometry (FTP): 3D shape measurement at 10,000 frames per second
Recent advances in imaging sensors and digital light projection technology
have facilitated a rapid progress in 3D optical sensing, enabling 3D surfaces
of complex-shaped objects to be captured with improved resolution and accuracy.
However, due to the large number of projection patterns required for phase
recovery and disambiguation, the maximum fame rates of current 3D shape
measurement techniques are still limited to the range of hundreds of frames per
second (fps). Here, we demonstrate a new 3D dynamic imaging technique, Micro
Fourier Transform Profilometry (FTP), which can capture 3D surfaces of
transient events at up to 10,000 fps based on our newly developed high-speed
fringe projection system. Compared with existing techniques, FTP has the
prominent advantage of recovering an accurate, unambiguous, and dense 3D point
cloud with only two projected patterns. Furthermore, the phase information is
encoded within a single high-frequency fringe image, thereby allowing
motion-artifact-free reconstruction of transient events with temporal
resolution of 50 microseconds. To show FTP's broad utility, we use it to
reconstruct 3D videos of 4 transient scenes: vibrating cantilevers, rotating
fan blades, bullet fired from a toy gun, and balloon's explosion triggered by a
flying dart, which were previously difficult or even unable to be captured with
conventional approaches.Comment: This manuscript was originally submitted on 30th January 1
Optical Technologies for UV Remote Sensing Instruments
Over the last decade significant advances in technology have made possible development of instruments with substantially improved efficiency in the UV spectral region. In the area of optical coatings and materials, the importance of recent developments in chemical vapor deposited (CVD) silicon carbide (SiC) mirrors, SiC films, and multilayer coatings in the context of ultraviolet instrumentation design are discussed. For example, the development of chemically vapor deposited (CVD) silicon carbide (SiC) mirrors, with high ultraviolet (UV) reflectance and low scatter surfaces, provides the opportunity to extend higher spectral/spatial resolution capability into the 50-nm region. Optical coatings for normal incidence diffraction gratings are particularly important for the evolution of efficient extreme ultraviolet (EUV) spectrographs. SiC films are important for optimizing the spectrograph performance in the 90 nm spectral region. The performance evaluation of the flight optical components for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument, a spectroscopic instrument to fly aboard the Solar and Heliospheric Observatory (SOHO) mission, designed to study dynamic processes, temperatures, and densities in the plasma of the upper atmosphere of the Sun in the wavelength range from 50 nm to 160 nm, is discussed. The optical components were evaluated for imaging and scatter in the UV. The performance evaluation of SOHO/CDS (Coronal Diagnostic Spectrometer) flight gratings tested for spectral resolution and scatter in the DGEF is reviewed and preliminary results on resolution and scatter testing of Space Telescope Imaging Spectrograph (STIS) technology development diffraction gratings are presented
Algorithms for compression of high dynamic range images and video
The recent advances in sensor and display technologies have brought upon the High Dynamic Range (HDR) imaging capability. The modern multiple exposure HDR sensors can achieve the dynamic range of 100-120 dB and LED and OLED display devices have contrast ratios of 10^5:1 to 10^6:1.
Despite the above advances in technology the image/video compression algorithms and associated hardware are yet based on Standard Dynamic Range (SDR) technology, i.e. they operate within an effective dynamic range of up to 70 dB for 8 bit gamma corrected images. Further the existing infrastructure for content distribution is also designed for SDR, which creates interoperability problems with true HDR capture and display equipment.
The current solutions for the above problem include tone mapping the HDR content to fit SDR. However this approach leads to image quality associated problems, when strong dynamic range compression is applied. Even though some HDR-only solutions have been proposed in literature, they are not interoperable with current SDR infrastructure and are thus typically used in closed systems.
Given the above observations a research gap was identified in the need for efficient algorithms for the compression of still images and video, which are capable of storing full dynamic range and colour gamut of HDR images and at the same time backward compatible with existing SDR infrastructure. To improve the usability of SDR content it is vital that any such algorithms should accommodate different tone mapping operators, including those that are spatially non-uniform.
In the course of the research presented in this thesis a novel two layer CODEC architecture is introduced for both HDR image and video coding. Further a universal and computationally efficient approximation of the tone mapping operator is developed and presented. It is shown that the use of perceptually uniform colourspaces for internal representation of pixel data enables improved compression efficiency of the algorithms. Further proposed novel approaches to the compression of metadata for the tone mapping operator is shown to improve compression performance for low bitrate video content. Multiple compression algorithms are designed, implemented and compared and quality-complexity trade-offs are identified. Finally practical aspects of implementing the developed algorithms are explored by automating the design space exploration flow and integrating the high level systems design framework with domain specific tools for synthesis and simulation of multiprocessor systems. The directions for further work are also presented
Random on-board pixel sampling (ROPS) X-ray Camera
Recent advances in compressed sensing theory and algorithms offer new
possibilities for high-speed X-ray camera design. In many CMOS cameras, each
pixel has an independent on-board circuit that includes an amplifier, noise
rejection, signal shaper, an analog-to-digital converter (ADC), and optional
in-pixel storage. When X-ray images are sparse, i.e., when one of the following
cases is true: (a.) The number of pixels with true X-ray hits is much smaller
than the total number of pixels; (b.) The X-ray information is redundant; or
(c.) Some prior knowledge about the X-ray images exists, sparse sampling may be
allowed. Here we first illustrate the feasibility of random on-board pixel
sampling (ROPS) using an existing set of X-ray images, followed by a discussion
about signal to noise as a function of pixel size. Next, we describe a possible
circuit architecture to achieve random pixel access and in-pixel storage. The
combination of a multilayer architecture, sparse on-chip sampling, and
computational image techniques, is expected to facilitate the development and
applications of high-speed X-ray camera technology.Comment: 9 pages, 6 figures, Presented in 19th iWoRI
Roadmap on optical security
Postprint (author's final draft
Applications of AFM in pharmaceutical sciences
Atomic force microscopy (AFM) is a high-resolution imaging technique that uses a small probe (tip and cantilever) to provide topographical information on surfaces in air or in liquid media. By pushing the tip into the surface or by pulling it away, nanomechanical data such as compliance (stiffness, Young’s Modulus) or adhesion, respectively, may be obtained and can also be presented visually in the form of maps displayed alongside topography images. This chapter outlines the principles of operation of AFM, describing some of the important imaging modes and then focuses on the use of the technique for pharmaceutical research. Areas include tablet coating and dissolution, crystal growth and polymorphism, particles and fibres, nanomedicine, nanotoxicology, drug-protein and protein-protein interactions, live cells, bacterial biofilms and viruses. Specific examples include mapping of ligand-receptor binding on cell surfaces, studies of protein-protein interactions to provide kinetic information and the potential of AFM to be used as an early diagnostic tool for cancer and other diseases. Many of these reported investigations are from 2011-2014, both from the literature and a few selected studies from the authors’ laboratories
Soliton microcomb based spectral domain optical coherence tomography
Spectral domain optical coherence tomography (SD-OCT) is a widely used and
minimally invaive technique for bio-medical imaging [1]. SD-OCT typically
relies on the use of superluminescent diodes (SLD), which provide a low-noise
and broadband optical spectrum. Recent advances in photonic chipscale frequency
combs [2, 3] based on soliton formation in photonic integrated microresonators
provide an chipscale alternative illumination scheme for SD-OCT. Yet to date,
the use of such soliton microcombs in OCT has not yet been analyzed. Here we
explore the use of soliton microcombs in spectral domain OCT and show that, by
using photonic chipscale Si3N4 resonators in conjunction with 1300 nm pump
lasers, spectral bandwidths exceeding those of commercial SLDs are possible. We
demonstrate that the soliton states in microresonators exhibit a noise floor
that is ca. 3 dB lower than for the SLD at identical power, but can exhibit
significantly lower noise performance for powers at the milliWatt level. We
perform SD-OCT imaging on an ex vivo fixed mouse brain tissue using the soliton
microcomb, alongside an SLD for comparison, and demonstrate the principle
viability of soliton based SD-OCT. Importantly, we demonstrate that classical
amplitude noise of all soliton comb teeth are correlated, i.e. common mode, in
contrast to SLD or incoherent microcomb states [4], which should, in theory,
improve the image quality. Moreover, we demonstrate the potential for circular
ranging, i.e. optical sub-sampling [5, 6], due to the high coherence and
temporal periodicity of the soliton state. Taken together, our work indicates
the promising properties of soliton microcombs for SD-OCT
Deep Thermal Imaging: Proximate Material Type Recognition in the Wild through Deep Learning of Spatial Surface Temperature Patterns
We introduce Deep Thermal Imaging, a new approach for close-range automatic
recognition of materials to enhance the understanding of people and ubiquitous
technologies of their proximal environment. Our approach uses a low-cost mobile
thermal camera integrated into a smartphone to capture thermal textures. A deep
neural network classifies these textures into material types. This approach
works effectively without the need for ambient light sources or direct contact
with materials. Furthermore, the use of a deep learning network removes the
need to handcraft the set of features for different materials. We evaluated the
performance of the system by training it to recognise 32 material types in both
indoor and outdoor environments. Our approach produced recognition accuracies
above 98% in 14,860 images of 15 indoor materials and above 89% in 26,584
images of 17 outdoor materials. We conclude by discussing its potentials for
real-time use in HCI applications and future directions.Comment: Proceedings of the 2018 CHI Conference on Human Factors in Computing
System
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