Multi-transmitter aperture synthesis is a method in which multiple transmitters can be used to improve resolution and contrast of distributed aperture systems. Such a system utilizes multiple transmitter locations to ...
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Multi-transmitter aperture synthesis is a method in which multiple transmitters can be used to improve resolution and contrast of distributed aperture systems. Such a system utilizes multiple transmitter locations to interrogate a target from multiple look angles thus increasing the angular spectrum content captured by the receiver aperture array. Furthermore, such a system can improve the contrast of sparsely populated receiver arrays by capturing field data in the region between sub-apertures by utilizing multiple transmitter locations. This paper discusses the theory behind multi-transmitter aperture synthesis and provides experimental verification that imagery captured using multiple transmitters will provide increased resolution.
We present ultra high speed optical coherence tomography (OCT) with multi-megahertz line rates and investigate the achievable image quality. The presented system is a swept source OCT setup using a Fourier domain mode...
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We present ultra high speed optical coherence tomography (OCT) with multi-megahertz line rates and investigate the achievable image quality. The presented system is a swept source OCT setup using a Fourier domain mode locked (FDML) laser. Three different FDML-based swept laser sources with sweep rates of 1, 2.6 and 5.2MHz are compared. Imaging with 4 spots in parallel quadruples the effective speed, enabling depth scan rates as high as 20.8 million lines per second. Each setup provides at least 98dB sensitivity and similar to 10 mu m resolution in tissue. High quality 2D and 3D imaging of biological samples is demonstrated at full scan speed. A discussion about how to best specify OCT imaging speed is included. The connection between voxel rate, line rate, frame rate and hardware performance of the OCT setup such as sample rate, analog bandwidth, coherence length, acquisition dead-time and scanner duty cycle is provided. Finally, suitable averaging protocols to further increase image quality are discussed. (C) 2010 Optical Society of America
On-axis digital holography (DH) is becoming widely used for its time-resolved three-dimensional (3D) imaging capabilities. A 3D volume can be reconstructed from a single hologram. DH is applied as a metrological tool ...
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On-axis digital holography (DH) is becoming widely used for its time-resolved three-dimensional (3D) imaging capabilities. A 3D volume can be reconstructed from a single hologram. DH is applied as a metrological tool in experimental mechanics, biology, and fluid dynamics, and therefore the estimation and the improvement of the resolution are current challenges. However, the resolution depends on experimental parameters such as the recording distance, the sensor definition, the pixel size, and also on the location of the object in the field of view. This paper derives resolution bounds in DH by using estimation theory. The single point resolution expresses the standard deviations on the estimation of the spatial coordinates of a point source from its hologram. Cramer-Rao lower bounds give a lower limit for the resolution. The closed-form expressions of the Cramer-Rao lower bounds are obtained for a point source located on and out of the optical axis. The influences of the 3D location of the source, the numerical aperture, and the signal-to-noise ratio are studied. (C) 2010 Optical Society of America
We report an imaging sensor capable of recording the optical properties of partially polarized light by monolithically integrating aluminum nanowire optical filters with a CCD imaging array. The imaging sensor, compos...
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We report an imaging sensor capable of recording the optical properties of partially polarized light by monolithically integrating aluminum nanowire optical filters with a CCD imaging array. The imaging sensor, composed of 1000 by 1000 imaging elements with 7.4 mu m pixel pitch, is covered with an array of pixel-pitch matched nanowire optical filters with four different orientations offset by 45 degrees. The polarization imaging sensor has a signal-to-noise ratio of 45dB and captures intensity, angle and degree of linear polarization in the visible spectrum at 40 frames per second with 300mW of power consumption. (c) 2010 Optical Society of America
algorithms have been developed for discriminating image signals on a background of bimodal Gaussoid pulse noise under conditions of complete a priori indeterminacy concerning the image-signal distribution. The algorit...
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algorithms have been developed for discriminating image signals on a background of bimodal Gaussoid pulse noise under conditions of complete a priori indeterminacy concerning the image-signal distribution. The algorithms are based on a new optimality criterion that combines the minimum of the unconditional skip probability with the maximum correct-detection probability at limited levels of unconditional false-alarm and correct-nondetection probabilities. The results of numerical studies of algorithms are presented that show that they are of higher quality than known nonoptimal procedures, as well as than the optimal algorithm under the condition of complete a priori signal indeterminacy. (C) 2010 Optical Society of America.
Background and Objectives: Several studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to nondestructively measure the severity of subsurface demineralization in ena...
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Background and Objectives: Several studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to nondestructively measure the severity of subsurface demineralization in enamel and dentin, track lesion progression over time and measure remineralization. The purpose of this study was to develop methods for the automated assessment of the depth and severity of demineralization in PS-OCT scans. Materials and Methods: Subsurface caries-like lesions of increasing depth and severity were produced in adjoining windows on 10 bovine enamel samples via exposure to demineralization for periods of 1-4 days. PS-OCT scans were acquired for each sample and analyzed using various methods to calculate the lesion depth and severity. Edge detection algorithms were most successful for measurement of the lesion depth for improved assessment of lesion severity. Results: Edge-finding algorithms were able to detect significant differences (P < 0.05) in the lesion depth and severity between each of the periods of demineralization and sound enamel. The lesion depth and mineral loss were also measured with polarized light microscopy and transverse microradiography after sectioning the teeth for comparison. Conclusions: This study demonstrates that the depth and severity of early lesions can be calculated automatically for rapid analysis of PS-OCT images. Lasers Surg. Med. 42:62-68, 2010. (C) 2010 Wiley-Liss, Inc.
A reflection hyperspectral imaging system covering a 350-1000 nm spectral range is realized by a UV-visible-nearIR Fourier transform imaging spectrometer. The system has a simple design and good spectral and spatial r...
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A reflection hyperspectral imaging system covering a 350-1000 nm spectral range is realized by a UV-visible-nearIR Fourier transform imaging spectrometer. The system has a simple design and good spectral and spatial resolving performance. Accurate and fast microspectroscopic measurement results on novel colloidal crystal beads demonstrate the system has practical potential for high-throughput molecular multiplex assays. (C) 2010 Optical Society of America
Analysis of image formation in a differential interference contrast (DIC) microscope and retrieval of the specimen's properties require calibration of its key parameters, viz. shear and bias. We present a method o...
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Analysis of image formation in a differential interference contrast (DIC) microscope and retrieval of the specimen's properties require calibration of its key parameters, viz. shear and bias. We present a method of measuring the shear and the bias of a DIC microscope from the interference fringes produced in the back focal plane of the objective. Previous approaches, which use calibrated specimens such as polystyrene or fluorescent beads, provide rather approximate measurements of shear or require a complex optical setup. The method presented is accurate, relies on simple image analysis, and does not require a specimen. We provide a succinct and accurate description of properties of Nomarski prisms to explain the rationale behind the method. (C) 2010 Optical Society of America
By combining dynamic mechanical testing with spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) performed at 1550 nm we are able to directly investigate for the first time changes within s...
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By combining dynamic mechanical testing with spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) performed at 1550 nm we are able to directly investigate for the first time changes within scattering technical materials during tensile and fracture tests. Spatially and temporally varying polarization patterns, due to defects and material inhomogeneities, were observed within bulk polymer samples and used to finally obtain - with the help of advanced image processing algorithms - quantitative maps of the evolving internal stress distribution. Furthermore, locally increased stress within fiber-reinforced composite materials was identified in situ with SD-PS-OCT to cause depolarizing sites of fiber-matrix debonding prior the onset of complete structural failure. (C) 2010 Optical Society of America
A 3D structured light sheet microscope using a four-faceted symmetric pyramid is presented. The sample is illuminated by the resulting four beam interference field. This approach combines advantages of standing wave a...
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A 3D structured light sheet microscope using a four-faceted symmetric pyramid is presented. The sample is illuminated by the resulting four beam interference field. This approach combines advantages of standing wave and structured illumination microscopy. Examples of micrographs of fluorescently labeled Chinese hamster ovary (CHO) cells as well as of the compound eyes of drosophila are shown and the optical sectioning ability of our system is demonstrated. The capabilities and the limitations of the scheme are discussed. (C) 2010 Optical Society of America
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