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Laser speckle contrast imaging (LSCI) has emerged over the past decade as a powerful, yet simple, method for imaging of blood flow dynamics in real time. The rapid adoption of LSCI for physiological studies is due to the relative ...
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Laser speckle contrast imaging (LSCI) has emerged over the past decade as a powerful, yet simple, method for imaging of blood flow dynamics in real time. The rapid adoption of LSCI for physiological studies is due to the relative ease and low cost of building an instrument as well as the ability to quantify blood flow changes with excellent spatial and temporal resolution. Although measurements are limited to superficial tissues with no depth resolution, LSCI has been instrumental in pre-clinical studies of neurological disorders as well as clinical applications including dermatological, neurosurgical and endoscopic studies. Recently a number of technical advances have been developed to improve the quantitative accuracy and temporal resolution of speckle imaging. This article reviews some of these recent advances and describes several applications of speckle imaging.
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Background: The most severe diabetic foot ulcers are those related with critical ischemia, which isprimarily diagnosed with non-invasive diagnostics. However, these diagnostics have several disadvantages. Forexample, they only pro...
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Background: The most severe diabetic foot ulcers are those related with critical ischemia, which isprimarily diagnosed with non-invasive diagnostics. However, these diagnostics have several disadvantages. Forexample, they only provide global indications of the (macro)level of ischemia. A potential solution can be foundin novel optical imaging techniques for local assessment of the microcirculation in diabetic foot ulcers. This reviewprovides an overview of these imaging techniques (Laser Doppler Perfusion Imaging, Laser Speckle ContrastImaging, Photoacoustic Imaging and Hyperspectral Imaging) and their applicability for the diagnostic assessmentof microcirculation in diabetic foot ulcers.Method: For each technique, the following parts are described: a) their technical background; b) general clinicalapplications; and, c) its application for microcirculation assessment in diabetic foot ulcers. Parts a-b are based ona narrative review of the literature, part c on a systematic review that was performed in the database Scopus,covering the period from January 1, 2000 to November 31, 2017.Results: Each of these techniques has specific advantages and disadvantages for imaging microcirculation. Potentialclinical use depends on measurement aims, and clinical relevance. However, none of the techniques has astrongly established clinical relevance yet: we found a limited number of publications describing clinical outcomes.Future research is needed to determine which technique is the most clinically relevant for the assessmentof microcirculation in diabetic foot ulcers.Conclusion: Although promising, the currently available novel optical techniques need to be further improvedtechnically and prospective trials are necessary to evaluate their clinical value.
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With the extension of the application domains for laser imaging radar, it is necessary to find a new technical way to obtain high technical performance and adaptive ability. In this paper, A new concept of digital receiver of lase...
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With the extension of the application domains for laser imaging radar, it is necessary to find a new technical way to obtain high technical performance and adaptive ability. In this paper, A new concept of digital receiver of laser imaging radar system is presented. This digital receiver is defined as a time varying parameter receiver which possesses large dynamics region and time domain filter. The receiver's mode, component structure as well as every function of its processing are described. The results and laboratorial data show the feasibility of digital reception. Also, it can exploit the inherent nature of laser imaging radar to obtain high probability of detection.
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Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These...
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Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These interactions encode the encountered Doppler phenomena within a random interference pattern imaged in widefield, known as laser speckle. Studies of neurovascular function and coupling with LSCI have benefited from the real-time characterization of functional dynamics in the laboratory setting through quantification of perfusion dynamics. While the technique has largely been relegated to acute small animal imaging, its scalability is being assessed and characterized for both chronic and clinical neurovascular imaging.
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The U.S. Army is actively pursuing 3D active imaging techniques using laser sources emitting at 1.5 μm. This eyesafe short wave infrared (SWIR) waveband is advantageous due to both the improved eye safety and atmospheric propagat...
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The U.S. Army is actively pursuing 3D active imaging techniques using laser sources emitting at 1.5 μm. This eyesafe short wave infrared (SWIR) waveband is advantageous due to both the improved eye safety and atmospheric propagation through obscurants. NVESD has several active programs in this area, which will be reviewed in this paper. These are: 1) single-pixel scanned imaging laser radar, 2) 2D gated SWIR imaging, and 3) 3D-flash laser radar. These systems are being evaluated for various targeting scenarios, including as potential payloads on unmanned air-vehicles, ground vehicles and other sensor suites. Applications include low-cost long-range target identification, identification of heavily obscured targets, obstacle avoidance, and high resolution imaging.
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Through the relative motion of ladar and object, inverse synthetic aperture ladar can form the virtual synthetic aperture and improve the imaging resolution. On the basis of coherent array detectors with the laser local oscillator...
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Through the relative motion of ladar and object, inverse synthetic aperture ladar can form the virtual synthetic aperture and improve the imaging resolution. On the basis of coherent array detectors with the laser local oscillator, the problem of laser synthetic aperture coherent imaging for micro-rotating objects is studied. Firstly, structure and parameters of the telescope system based on the diffractive optical system are introduced. Then, the signal model of the imaging method is built, the imaging method is proposed, and influence of noise is analyzed. Afterwards, the signal model of the vibrating object is established and the vibration phase compensation method is proposed. The imaging method proposed forms a virtual aperture through micro-rotation of the object, and realizes high-resolution imaging in the pitch direction and azimuth direction. Without transmitting or processing broadband signals, the imaging system is easy to realize in engineering, and simulation results verify the effectiveness of the imaging method. Meanwhile, Fourier ptychography in the far-field condition is analyzed, and characteristics of the two methods are compared. It is concluded that the imaging method proposed belongs to the concept of traditional matched filter coherent imaging while far-field Fourier ptychography is classified into the category of super-resolution imaging.
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We present a method of three-dimensional particle velocimetry with a single digital colour camera using multiple colour illumination to encode image depth over a large volume. A copper vapour laser operating at 511 nm is used to p...
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We present a method of three-dimensional particle velocimetry with a single digital colour camera using multiple colour illumination to encode image depth over a large volume. A copper vapour laser operating at 511 nm is used to pump an optical fibre producing a multiple-wavelength beam via multiple order stimulated Raman scattering. The beam is dispersed and formed into a stack of thin sheets to illuminate a volume of space. The spatial co-ordinates of particles imaged within the illuminated volume are obtained from their imaged x,y positions with depth discerned from particle hue (set by the wavelength of illumination). The method exhibits an RMS depth error of 3% in relation to the thickness of the illuminated region. This paper reports a proof-of-principle of three-dimensional particle imaging using a multi-wavelength laser source with a view to 3D-3C particle velocimetry.
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This paper presents a time-to-digital converter/analog-to-digital-converter (TDC/ADC) hybrid LiDAR system-on-chip (SoC) to realize reliable self-driving systems. The smart accumulation technique (SAT) is proposed to achieve both 2...
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This paper presents a time-to-digital converter/analog-to-digital-converter (TDC/ADC) hybrid LiDAR system-on-chip (SoC) to realize reliable self-driving systems. The smart accumulation technique (SAT) is proposed to achieve both 200-m and high-pixel-resolution range imaging, which was untrodden with conventional LiDARs. The “smart” accumulation is realized by a simple object recognition strategy with small circuit overhead. When compared to conventional accumulations, the LiDAR range is enhanced without degrading the pixel resolution. Moreover, a TDC/ADC hybrid architecture is proposed to achieve a wide-distance-range LiDAR with a small silicon area and short-range precision. To minimize the ADC cost, a residue-quantizing noise-shaping (RQNS) SAR ADC is proposed. The prototype LiDAR SoC is fabricated in the 28-nm CMOS technology and integrated into the silicon photomultiplier (SiPM)-based LiDAR system. LiDAR measured with 240 × 96 pixels at 10 frames/s achieves a measurement range of 200 m with a 70-klx direct sunlight: the measurement range is 2× longer than conventional designs. Furthermore, our LiDAR achieves 4× higher effective pixel resolution compared to conventional designs using simple accumulation. A 3-D point-cloud image acquired with a real-life environment is presented.
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Previously published data demonstrate that the temporal processing algorithm for laser speckle contrast imaging (LSCI) can improve the visibility of deep blood vessels and is less susceptible to static speckle artifacts when compa...
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Previously published data demonstrate that the temporal processing algorithm for laser speckle contrast imaging (LSCI) can improve the visibility of deep blood vessels and is less susceptible to static speckle artifacts when compared with the spatial algorithm. To the best of our knowledge, the extent to which the temporal algorithm can accurately predict the speckle contrast associated with flow in deep blood vessels has not been quantified. Here, we employed two phantom systems and imaging setups (epi-illuminatJon and transillu-mination) to study the contrast predicted by the spatial and temporal algorithms in subsurface capillary tubes as a function of the camera exposure time and the actual flow speed. Our data with both imaging setups suggest that the contrast predicted by the temporal algorithm, and therefore the relative flow speed, is nearly independent of the degree of static optical scattering that contributes to the overall measured speckle pattern. Collectively, these results strongly suggest the potential of temporal LSCI at a single-exposure time to assess accurately the changes in blood flow even in the presence of substantial static optical scattering.
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