2,200 research outputs found
Field deployable dynamic lighting system for turbid water imaging
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2011The ocean depths provide an ever changing and complex imaging environment.
As scientists and researches strive to document and study more remote and
optically challenging areas, specifically scatter-limited environments. There is a
requirement for new illumination systems that improve both image quality and
increase imaging distance.
One of the most constraining optical properties to underwater image quality are
scattering caused by ocean chemistry and entrained organic material. By
reducing the size of the scatter interaction volume, one can immediately improve
both the focus (forward scatter limited) and contrast (backscatter limited) of
underwater images. This thesis describes a relatively simple, cost-effective and
field-deployable low-power dynamic lighting system that minimizes the scatter
interaction volume with both subjective and quantifiable improvements in imaging
performance
Single-photon detection techniques for underwater imaging
This Thesis investigates the potential of a single-photon depth profiling system for
imaging in highly scattering underwater environments. This scanning system measured
depth using the time-of-flight and the time-correlated single-photon counting (TCSPC)
technique. The system comprised a pulsed laser source, a monostatic scanning
transceiver, with a silicon single-photon avalanche diode (SPAD) used for detection of
the returned optical signal.
Spectral transmittance measurements were performed on a number of different water
samples in order to characterize the water types used in the experiments. This identified
an optimum operational wavelength for each environment selected, which was in the
wavelength region of 525 - 690 nm. Then, depth profiles measurements were performed
in different scattering conditions, demonstrating high-resolution image re-construction
for targets placed at stand-off distances up to nine attenuation lengths, using average
optical power in the sub-milliwatt range. Depth and spatial resolution were investigated
in several environments, demonstrating a depth resolution in the range of 500 μm to a
few millimetres depending on the attenuation level of the medium. The angular
resolution of the system was approximately 60 μrad in water with different levels of
attenuation, illustrating that the narrow field of view helped preserve spatial resolution
in the presence of high levels of forward scattering.
Bespoke algorithms were developed for image reconstruction in order to recover depth,
intensity and reflectivity information, and to investigate shorter acquisition times,
illustrating the practicality of the approach for rapid frame rates. In addition, advanced
signal processing approaches were used to investigate the potential of multispectral
single-photon depth imaging in target discrimination and recognition, in free-space and
underwater environments. Finally, a LiDAR model was developed and validated using
experimental data. The model was used to estimate the performance of the system under
a variety of scattering conditions and system parameters
3D LIDAR imaging using Ge-on-Si single–photon avalanche diode detectors
We present a scanning light detection and ranging (LIDAR) system incorporating an individual Ge-on-Si single-photon avalanche diode (SPAD) detector for depth and intensity imaging in the short-wavelength infrared region. The time-correlated single-photon counting technique was used to determine the return photon time-of-flight for target depth information. In laboratory demonstrations, depth and intensity reconstructions were made of targets at short range, using advanced image processing algorithms tailored for the analysis of single–photon time-of-flight data. These laboratory measurements were used to predict the performance of the single-photon LIDAR system at longer ranges, providing estimations that sub-milliwatt average power levels would be required for kilometer range depth measurements
Quantum-inspired computational imaging
Computational imaging combines measurement and computational methods with the aim of forming images even when the measurement conditions are weak, few in number, or highly indirect. The recent surge in quantum-inspired imaging sensors, together with a new wave of algorithms allowing on-chip, scalable and robust data processing, has induced an increase of activity with notable results in the domain of low-light flux imaging and sensing. We provide an overview of the major challenges encountered in low-illumination (e.g., ultrafast) imaging and how these problems have recently been addressed for imaging applications in extreme conditions. These methods provide examples of the future imaging solutions to be developed, for which the best results are expected to arise from an efficient codesign of the sensors and data analysis tools.Y.A. acknowledges support from the UK Royal Academy of Engineering under the Research Fellowship Scheme (RF201617/16/31). S.McL. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grant EP/J015180/1). V.G. acknowledges support from the U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office award W911NF-10-1-0404, the U.S. DARPA REVEAL program through contract HR0011-16-C-0030, and U.S. National Science Foundation through grants 1161413 and 1422034. A.H. acknowledges support from U.S. Army Research Office award W911NF-15-1-0479, U.S. Department of the Air Force grant FA8650-15-D-1845, and U.S. Department of Energy National Nuclear Security Administration grant DE-NA0002534. D.F. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grants EP/M006514/1 and EP/M01326X/1). (RF201617/16/31 - UK Royal Academy of Engineering; EP/J015180/1 - UK Engineering and Physical Sciences Research Council; EP/M006514/1 - UK Engineering and Physical Sciences Research Council; EP/M01326X/1 - UK Engineering and Physical Sciences Research Council; W911NF-10-1-0404 - U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office; HR0011-16-C-0030 - U.S. DARPA REVEAL program; 1161413 - U.S. National Science Foundation; 1422034 - U.S. National Science Foundation; W911NF-15-1-0479 - U.S. Army Research Office; FA8650-15-D-1845 - U.S. Department of the Air Force; DE-NA0002534 - U.S. Department of Energy National Nuclear Security Administration)Accepted manuscrip
A Review on Methods of Identifying and Counting Aedes Aegypti Larvae using Image Segmentation Technique
Aedes aegypti mosquitoes are a small slender fly insect that spreads the arbovirus from flavivirus vector through its sucking blood. An early detection of this species is very important because once these species turn into adult mosquitoes a population control becomes more complicated. Things become worse when difficult access places like water storage tank becomes one of the breeding favorite places for Aedes aegypti mosquitoes. Therefore, there is a need to help the field operator during the routine inspection for an automated identification and detection of Aedes aegypti larvae, especially at difficult access places. This paper reviews different methodologies that have been used by various researchers in identifying and counting Aedes aegypti. The objective of the review was to analyze the techniques and methods in identifying and counting the Aedes Aegypti larvae of various fields of study from 2008 and above by taking account their performance and accuracy. From the review, thresholding method was the most widely used with high accuracy in image segmentation followed by hidden Markov model, histogram correction and morphology operation region growing
Imaging through obscurants using time-correlated single-photon counting in the short-wave infrared
Single-photon time-of-flight (ToF) light detection and ranging (LiDAR) systems have
emerged in recent years as a candidate technology for high-resolution depth imaging in
challenging environments, such as long-range imaging and imaging in scattering media.
This Thesis investigates the potential of two ToF single-photon depth imaging systems
based on the time-correlated single-photon (TCSPC) technique for imaging targets in
highly scattering environments. The high sensitivity and picosecond timing resolution
afforded by the TCSPC technique offers high-resolution depth profiling of remote targets
while maintaining low optical power levels. Both systems comprised a pulsed picosecond
laser source with an operating wavelength of 1550 nm, and employed InGaAs/InP SPAD
detectors. The main benefits of operating in the shortwave infrared (SWIR) band include
improved atmospheric transmission, reduced solar background, as well as increased laser
eye-safety thresholds over visible band sensors.
Firstly, a monostatic scanning transceiver unit was used in conjunction with a
single-element Peltier-cooled InGaAs/InP SPAD detector to attain sub-centimetre
resolution three-dimensional images of long-range targets obscured by camouflage
netting or in high levels of scattering media. Secondly, a bistatic system, which employed
a 32 × 32 pixel format InGaAs/InP SPAD array was used to obtain rapid depth profiles
of targets which were flood-illuminated by a higher power pulsed laser source. The
performance of this system was assessed in indoor and outdoor scenarios in the presence
of obscurants and high ambient background levels.
Bespoke image processing algorithms were developed to reconstruct both the depth and
intensity images for data with very low signal returns and short data acquisition times,
illustrating the practicality of TCSPC-based LiDAR systems for real-time image
acquisition in the SWIR wavelength region - even in the photon-starved regime.The Defence Science and Technology Laboratory ( Dstl) National PhD Schem
Underwater image restoration: super-resolution and deblurring via sparse representation and denoising by means of marine snow removal
Underwater imaging has been widely used as a tool in many fields, however, a major issue is the quality of the resulting images/videos. Due to the light's interaction with water and its constituents, the acquired underwater images/videos often suffer from a significant amount of scatter (blur, haze) and noise. In the light of these issues, this thesis considers problems of low-resolution, blurred and noisy underwater images and proposes several approaches to improve the quality of such images/video frames.
Quantitative and qualitative experiments validate the success of proposed algorithms
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