Showing papers in "Proceedings of SPIE in 1993"
TL;DR: In this paper, a general and useful formalism has been developed for defining the transverse beam quality as well as other propagation parameters of arbitrary real laser beams, and a convenient new instrument for measuring the propagation parameters and beam quality measurements on various types of laser devices.
Abstract: This paper will review a very general and useful formalism that has recently been developed for defining the transverse beam quality as well as other propagation parameters of arbitrary real laser beams. We also describe a convenient new instrument for measuring the propagation parameters of high-power laser beams, and summarize some results of beam quality measurements on various types of laser devices.
239 citations
TL;DR: The moderate resolution imaging spectroradiometer (MODIS) is a scanning radiometer that will fly as a facility instrument on the NASA polar-orbiting earth observing system (EOS) spacecraft.
Abstract: The moderate resolution imaging spectroradiometer (MODIS) is a scanning radiometer that will fly as a facility instrument on the NASA polar-orbiting earth observing system (EOS) spacecraft. The first MODIS instrument is scheduled for launch in 1998 on the first EOS-AM spacecraft. MODIS is designed to provide critical data necessary to monitor global change and provide information vital to understanding the Earth as a system. This paper provides an overview of the MODIS requirements and system design. The operation of the instrument is described from photons in to formatted data out. Brief descriptions of the key functional subsystems of the instrument are provided. Predicted performance is summarized for critical areas including radiometric sensitivity and calibration accuracy, modulation transfer function pointing accuracy, and spectral band registration.
230 citations
TL;DR: In this article, a morphology-based algorithm has been developed for point target detection in IRST applications, which has an efficient computational paradigm based on combinations of simple nonlinear grayscale operations.
Abstract: A morphology-based algorithm has been developed for point target detection in IRST applications. It exhibits comparable detection and false alarm performance to a median filter. The morphology-based algorithm has an efficient computational paradigm based on combinations of simple nonlinear grayscale operations, which makes it ideally suited to real- time, high data rate IRST applications. A detection filter based on morphological background estimation exhibits spatial high-pass characteristics emphasizing target-like peaks in the data and suppressing all other clutter. Example cases are presented which point out the detection performance differences between the morphological and median approaches. Overall performance results were generated in the form of ROC curves for cloud, horizon and sea clutter IRAMMP backgrounds.
219 citations
TL;DR: In this paper, a 1 - 5.4 micrometers Cryogenic Echelle Spectrograph (CSHELL) for the NASA Infrared Telescope Facility is described, which operates in a single-order long-slit mode, and a circular variable filter is used as an order sorter.
Abstract: A 1 - 5.4 micrometers Cryogenic Echelle Spectrograph (CSHELL) for the NASA Infrared Telescope Facility is described. It achieves a resolving power of 5,000 to 40,000 using slits ranging from 4.0' to 0.5' in width and 30' long. It operates in a single-order long-slit mode, and a circular variable filter is used as an order sorter. Two infrared arrays are employed to achieve spectral coverage from 1 - 5.4 micrometers : a 256 X 256 HgCdTe NICMOS-3 array for 1 - 2.5 micrometers and a SBRC 58 X 62 InSb array for 2.8 - 5.4 micrometers . A closed- cycle cooler is employed to keep the optics and supporting structure at 73 K and to maintain the detectors at their proper operating temperatures. The entire spectrograph fits within an envelope of 64 cm X 35 cm X 27 cm. The instrument is controlled by a microcomputer mounted on the telescope, but the observer commands the instrument from a UNIX X Windows workstation on the Internet. This use of the Internet for communication between instrument control and user interface computers facilitates remote observing. A limiting magnitude of 12.3 mag is achieved for S/N equals 10 in 1 hour integration time, at resolving power of 20,000 at 2.2 micrometers wavelength.
186 citations
TL;DR: The FBI has recently adopted a standard for the compression of digitized 8-bit gray-scale fingerprint images based on scalar quantization of a 64-subband discrete wavelet transform decomposition of the images, followed by Huffman coding.
Abstract: The FBI has recently adopted a standard for the compression of digitized 8-bit gray-scale fingerprint images. The standard is based on scalar quantization of a 64-subband discrete wavelet transform decomposition of the images, followed by Huffman coding. Novel features of the algorithm include the use of symmetric boundary conditions for transforming finite- length signals and a subband decomposition tailored for fingerprint images scanned at 500 dpi. The standard is intended for use in conjunction with ANSI/NBS-CLS 1-1993, American National Standard Data Format for the Interchange of Fingerprint Information, and the FBI's Integrated Automated Fingerprint Identification System.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
183 citations
TL;DR: In this article, a rigorous technique using a Monte Carlo model has been developed to determine the optical properties of biological tissue from goniometer and integrating sphere measurements, using these techniques, the wavelength dependence of the phase function, g-value, absorption coefficient, scattering and reduced scattering coefficient were determined for postmortem neonate and adult human brain tissue over the wavelength range of 500 to 1000 nm.
Abstract: A rigorous technique using a Monte Carlo model has been developed to determine the optical properties of biological tissue from goniometer and integrating sphere measurements. Using these techniques, the wavelength dependence of the phase function, g-value, absorption coefficient, scattering and reduced scattering coefficient were determined for postmortem neonate and adult human brain tissue over the wavelength range of 500 to 1000 nm. Single scattering phase functions as a function of wavelength have been measured using a goniometer system and optically thin tissue slices. Spectra for the absorption and scattering coefficients have been determined from a set of integrating sphere measurements, using a white light source and a CCD spectrometer. The integrating sphere data were analyzed using a novel Monte Carlo inversion technique, which makes use of the measured phase functions and which takes into account the effects of sample geometry and the angular dependence of specular reflection. This method overcomes some of the problems and shortfalls of the analytical techniques which employ Kubelka Munk or diffusion theory. The reduced scattering coefficients for all types of brain tissue showed a linear decrease with increasing wavelength. The wavelength dependence of the scattering coefficient and the phase function is shown to be considerable, and cannot be neglected.
165 citations
TL;DR: In a separate study, in vivo optical reflectance spectrophotometry was performed on human breast tumors implanted intramuscularly and subcutaneously in nineteen nude mice, and the validity of applying a quadruple wavelength breast cancer discrimination metric to the in vivo condition was tested.
Abstract: A new technique called Ultrasound Tagging of Light (UTL) for imaging breast tissue is described. In this approach, photon localization in turbid tissue is achieved by cross- modulating a laser beam with focussed, pulsed ultrasound. Light which passes through the ultrasound focal spot is `tagged' with the frequency of the ultrasound pulse. The experimental system uses an Argon-Ion laser, a single PIN photodetector, and a 1 MHz fixed-focus pulsed ultrasound transducer. The utility of UTL as a photon localization technique in scattering media is examined using tissue phantoms consisting of gelatin and intralipid. In a separate study, in vivo optical reflectance spectrophotometry was performed on human breast tumors implanted intramuscularly and subcutaneously in nineteen nude mice. The validity of applying a quadruple wavelength breast cancer discrimination metric (developed using breast biopsy specimens) to the in vivo condition was tested. A scatter diagram for the in vivo model tumors based on this metric is presented using as the `normal' controls the hands and fingers of volunteers. Tumors at different growth stages were studied; these tumors ranged in size from a few millimeters to two centimeters. It is expected that when coupled with a suitable photon localization technique like UTL, spectral discrimination methods like this one will prove useful in the detection of breast cancer by non-ionizing means.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
157 citations
TL;DR: HYDICE (the Hyperspectral Digital Imagery Collection Experiment) is a program to build and operate an advanced airborne imaging spectrometer that will provide high quality hyperspectral data for use by a number of US civil agencies in determining its utility for a wide range of applications.
Abstract: HYDICE (the Hyperspectral Digital Imagery Collection Experiment) is a program to build and operate an advanced airborne imaging spectrometer Scheduled to be operating in 1994, it will provide high quality hyperspectral data for use by a number of US civil agencies in determining its utility for a wide range of applications, as well as in support of basic research The current status of the system under construction and plans for its operation are reviewed
136 citations
TL;DR: In this article, the properties of avalanche photodiodes and associated electronics required for photon counting in the Geiger and the sub-Geiger modes are reviewed, and the results obtained by using an active-mode fast quench circuit capable of switching overvoltages as high as 15 V with a dead time of less than 50 ns are reported.
Abstract: The properties of avalanche photodiodes and associated electronics required for photon counting in the Geiger and the sub-Geiger modes are reviewed. When the Geiger mode is used, there are significant improvements reported in overall photon detection efficiencies (approaching 70% at 633 nm), and a timing jitter (under 200 ps) is achieved with passive quenching at high overvoltages (20-30 V). The results obtained by using an active-mode fast quench circuit capable of switching overvoltages as high as 15 V (giving photon detection efficiencies in the 50% range) with a dead time of less than 50 ns are reported. Larger diodes (up to 1 mm in diameter) that are usable in the Geiger mode and that have quantum efficiencies over 80% in the 500-800-nm range are also reported.
127 citations
TL;DR: Topography is one of the fundamental measurements required to understand the structure and evolution of planetary bodies as mentioned in this paper, and topographic data constitute an important input into a variety of studies in geophysics, geology, and atmospheric circulation.
Abstract: Surface topography is one of the fundamental measurements required to understand the structure and evolution of planetary bodies. Specifically, topographic data constitute an important input into a variety of studies in geophysics, geology, and atmospheric circulation. Topog raphic measurements with long-wavelength integrity provide a basis for interpreting the gravity field and determining the internal structure, state of stress and isostatic compensation of planetary lithospheres. Regional-scale topography and derived topographic gradients are required in geological investigations of fluid and lava flow, erosion, volcanic and impact processes. In addition, topography provides an important constraint on global atmospheric circulation models.
125 citations
TL;DR: In this paper, a technique for the measurement of optical properties in clear and turbid media based on time-resolved detection of acoustic transients was described for measuring the absorption and scattering properties of tissue.
Abstract: A technique is described for the measurement of optical properties in clear and turbid media based on time-resolved detection of acoustic transients. Thermal expansion of the irradiated volume of a sample heated by short laser pulses causes a pressure-rise that is proportionally to the laser fluence and the absorption coefficient in the sample. The exponential profile of the acoustic signal formed by the initial stress distribution corresponds to z-axial light distribution in the irradiated volume. Therefore, the absorption and scattering properties of tissue can be determined from the profile and amplitude of the acoustic signals induced by the laser pulses. Stress waves generated in phantom aqueous medium and biological tissues by laser pulses were detected by a broad-band lithium niobate acoustic transducer. The results indicate that absorption coefficients in soft biological tissues in the near infrared spectral range are significantly (5 - 10 times) lower as compared to previously reported from integrating sphere measurements.
TL;DR: In this article, a set of algorithms were described to estimate aerosol optical depth, atmospheric water vapor, and surface pressure height from the AVIRIS measured radiance using a radiative transfer code.
Abstract: The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is an imaging spectrometer that measures spatial images of the total up welling spectral radiance from 400 to 2500 nm at 10 nm spectral intervals. Quantitative research and application objectives for surface investigations require conversion of the measured radiance to surface reflectance or surface leaving radiance. To calculate apparent surface reflectance an estimation of aerosol optical depth is required for compensation of aerosol scattering and absorption across the spectral range. Determination of other atmospheric characteristics such as atmospheric water vapor and surface pressure is also required. In this paper we describe a set of algorithms to estimate aerosol optical depth, atmospheric water vapor, and surface pressure height from the AVIRIS measured radiance. Based upon these determined atmospheric parameters we described an algorithm to calculated apparent surface reflectance from the AVIRIS measured radiance using a radiative transfer code.
TL;DR: A system employing an infrared optical digitizer to indicate position on either CT, MRI, or PET scans, consisting of a base ring attached to the patient's head during surgery, hand held instruments of any type, a camera array, and a computer display.
Abstract: Frame based stereotactic surgery allows the surgeon to precisely approach a predetermined target. Although useful for diagnostic and functional procedures, mechanical instruments fail to indicate position quickly during open craniotomy. We have developed a system employing an infrared optical digitizer to indicate position on either CT, MRI, or PET scans. The system consists of a base ring attached to the patient's head during surgery, hand held instruments of any type, a camera array, and a computer display. Light emitting diodes on the instruments and head ring are tracked by three linear CCDs suspended over the surgical field. The position of the surgical instrument relative to the patient's head is computed by a personal computer. Surgical position is indicated on an individual CT, MRI, or PET slice. A graphics workstation provides three dimensional display of position.
TL;DR: It is concluded that both line-fitting and Fowler- sampling are the best sampling methods covering the whole performance regime, providing large improvement in the read-noise dominated regime and approaching CDS capability in the photon-no noise dominated regime.
Abstract: The newest 256 X 256 InSb arrays (CRC-590 and CRC-463 multiplexers) from Santa Barbara Research Center have reached a milestone in low noise performance. Using the Fowler-sampling technique to acquire data, we have achieved 10 - 13 e - multiply sample read-out (MSR) noise with the new arrays. With this remarkably low noise performance, background limited performance occurs at relatively small signal levels, viz. a few percent of full-well depth. The signal-to-noise capability of infrared detectors operating in both read noise and background limited performance is an important parameter for evaluating the efficacy of various data sampling methods. We conclude that both line-fitting and Fowler- sampling are the best sampling methods covering the whole performance regime, providing large improvement in the read-noise dominated regime and approaching CDS capability in the photon-noise dominated regime.
TL;DR: In this article, the reflectance-based method is used to determine an absolute radiometric calibration of Landsat-5 Thematic Mapper for the solar reflective portion of the spectrum.
Abstract: The reflectance-based method is used to determine an absolute radiometric calibration of Landsat-5 Thematic Mapper for the solar reflective portion of the spectrum. Results are given for data collected at White Sands Missile Range in New Mexico on 1992-08-15. These results are compared to those obtained from applying a similar processing approach to data collected in 1984, 1985, 1987, and 1988.
TL;DR: In this paper, the effects of the focal spot size and collection angle on the heterodyne efficiency for light backscattered over a range of sampling depths were investigated using a single-backscatter model of a turbid biological sample.
Abstract: Reflectometers based on low-coherence interferometry are potentially useful tools for probing superficial biological structures. In this paper, we present results of theoretical and experimental investigations of the variables that affect the backscattered signals measured by low-coherence reflectometers from dense tissues. Using a single-backscatter model of a turbid biological sample, we examine the effects of the focal spot size and collection angle on the heterodyne efficiency for light backscattered over a range of sampling depths. Coherence losses resulting from multiple scattering are studied using a simple analytical model augmented by numerical simulations. Our results suggest that the single-backscatter model, which has been applied previously in atmospheric lidar and ultrasound studies, provides a good description of the relationship between the shape of the reflectance-vs-depth profiles and the optical properties of a turbid sample under certain conditions. Model predictions were tested by measuring reflectance profiles from dense suspensions of particles using a low-coherence reflectometer built in our laboratory and a commercially available fiber-optic reflectometer. Results of these measurements are compared with others obtained in vivo from human skin. To demonstrate that small structures located at depths of several hundred microns can be probed without contacting a biological specimen, we show an image of bone specimen obtained with the laboratory reflectometer.
TL;DR: The problem of intelligent use of sensors in a multi-sensor, multi-target surveillance system is discussed and the particular assignment of tracks to sensors that maximizes the total information gain subject to the constraints on the sensors is generated using linear programming methods.
Abstract: The problem of intelligent use of sensors in a multi-sensor, multi-target surveillance system is discussed. The problem is to make the optimal assignment of targets to sensors subject to given constraints on sensor capacity and for a given definition of optimal. We have found previous work on the sensor management problem to have deficiencies due to the way information is used to optimize the assignment. There are numerous formulations of such `information' based approaches in the literature. This paper attempts to put the problem on a first principles basis. The approach taken here it to determine the predicted gain in information content of a track j after it is updated with data from sensor i for all pairs i,j. This information content can be predicted without making the actual observation by using the properties of the Kalman covariance matrix. The particular assignment of tracks to sensors that maximizes the total information gain subject to the constraints on the sensors is then generated using linear programming methods.
TL;DR: In this article, the authors investigated a continuous, thermally driven microexplosion type of laser ablation based on the inhomogeneous distribution of strong (water) and weak absorbers (hydroxyapatite).
Abstract: Er:YAG laser ablation was investigated by fast photography in a Schlieren optic setup. The results support the idea of continuous, thermally driven microexplosion type of ablation, which is based on the inhomogeneous distribution of strong (water) and weak absorbers (hydroxyapatite). Sudden vaporization and heating of the water content leads to a very effective material removal by bursting off the solid tissue components. Material is ejected in the form of particles when the threshold energy density for ablation (about 3 J cm-2) is reached. For high radiant exposure, initial plume velocity is in the order of the speed of sound in air. After leaving the tissue surface, particles are heated by the still incoming laser radiation, causing glowing and melting. No surface plasma and only weak pressure waves caused by individual spikes were observed.
TL;DR: In this article, various characteristics of photon diffusion process in biological tissues are examined for the following geometries: (1) a semi-infinite homogeneous medium, (2) a homogeneous slab with thickness d equals 10 mm, and (3) an infinite host medium containing an inclusion object of different optical properties, using a Monte Carlo (MC) simulation technique.
Abstract: Various characteristics of photon diffusion process in biological tissues are examined for the following geometries: (1) a semi-infinite homogeneous medium, (2) a homogeneous slab with thickness d equals 10 mm, and (3) an infinite host medium containing an inclusion object of different optical properties, using a Monte Carlo (MC) simulation technique. Our simulation results are compared with both the diffusion theory and a discrete lattice model (when applicable). We discuss the applicability of using MC simulations as a means to characterize absorbing objects in realistic biological tissue systems.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The Ohio State Infrared Imager/Spectrometer (OSIRIS) is a general purpose near infrared (0.9 to 2.5 micrometers ) instrument that can be used at a wide variety of telescope focal planes as mentioned in this paper.
Abstract: The Ohio State Infrared Imager/Spectrometer (OSIRIS) is a general purpose near infrared (0.9 to 2.5 micrometers ) instrument that can be used at a wide variety of telescope focal planes. OSIRIS currently uses a 256 X 256 HgCdTe array detector and will accommodate larger arrays when available. OSIRIS has two modes of operation: imaging and spectroscopic. This paper describes the general instrument design and sample scientific results.
TL;DR: Cylinders of microfil light-cured composite resin were bonded to the labial enamel surface of bovine incisor teeth which had previously been subjected to different laser treatments, and the tensile strength reached 92.5% of the acid etched bonding.
Abstract: Cylinders of microfil light-cured composite resin were bonded to the labial enamel surface of bovine incisor teeth which had previously been subjected to different laser treatments. One part of the tooth surfaces were laser treated in a defocused way only, another part with a different overlaying pattern of focused laser pulses. Specimens were thermocycled and the adhesion of the composites were determined by tensile strength tests. The best results were obtained by laser conditioning of the enamel surface in a defocused way with an overlaying fine pattern of focused single shots. The tensile strength reached 92.5% of the acid etched bonding.
TL;DR: UCSD's IR astronomy group is building an imaging mid-IR spectrometer for the Keck Telescope, which is built around a 96 X 96 element, Si:As impurity band conduction array built by GenCorp Aerojet Electronics Systems Division as discussed by the authors.
Abstract: UCSD's IR astronomy group is building an imaging mid-IR spectrometer for the Keck Telescope. This instrument, the Long-Wavelength Spectrometer (LWS), is built around a 96 X 96 element, Si:As impurity band conduction array built by GenCorp Aerojet Electronics Systems Division. The LWS has low and moderate spectroscopy modes with nominal spectral resolutions of R (equals (lambda) /(Delta) (lambda) ) equals 100 and 1400 respectively, operating in the 10 micrometers (second order) and 20 micrometers (first order) ground- based atmospheric spectral windows. The LWS is also capable of direct imaging from 5 micrometers to 27 micrometers through a selection of 16 filters. For each of the spectroscopic modes and the direct imaging mode, the plate scale is 0.12 arcsec/pixel, which Nyquist samples the telescope's diffraction pattern at 10 micrometers . Because of the large light gathering power of the Keck Telescope and it's small diffraction pattern, the LWS will have unparalleled point source sensitivity, making it the premiere instrument for extragalactic and general faint-source mid-IR spectroscopy.
TL;DR: In the amide III region, the protein spectrum is better resolved into individual bands than in amide I region, which allows for a greater ease in peak definement of the protein spectra as discussed by the authors.
Abstract: Protein secondary structure has been analyzed using a Fourier transform infrared spectroscopic method in the amide III region. Although extensive work has been done on protein secondary structure using the amide I region (1700 - 1600 cm-1), the amide III region has not been utilized in the past for its potential in protein structural analysis. One of the major reasons for non-use of the amide III vibrations is perhaps the very weak signal in the amide III frequency region (1200 - 1350 cm-1). However, benefits of using the amide III region are substantial. For example, water vibrations do not interfere with the protein spectrum unlike in the amide I region. In the amide III region, the protein spectrum is better resolved into individual bands than in the amide I region. This feature allows for a greater ease in peak definement of the protein spectra. In the amide III region, the bands for the individual secondary structures ((alpha) -helix, (beta) -sheet and random coils) do not overlap as much as they do in the amide I region. This lack of overlapping allows for easier and a more reliable means of peak assignment, and secondary structure band positions are easier to determine. Amide III region of protein IR spectra appears to be a valuable tool in estimating the amount of secondary structure present in proteins.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, four basic approaches: regression, knowledge-based, inversion, and combinations of remotely sensed data and water balance models are discussed. But none of these methods are suitable for ground-based and aircraft experiments.
Abstract: Methods for estimating profile soil moisture using remotely sensed surface moisture data are reviewed. Primary attention is given to four basic approaches: regression, knowledge-based, inversion, and combinations of remotely sensed data and water balance models. Results of ground-based and aircraft experiments using microwave radiometers for soil moisture measurements are discussed to illustrate the methods.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The physical basis for figures of merit which a nonlinear material must satisfy in order for it to be useful for all-optical switching in waveguides (as well as other nonlinear devices).
Abstract: It is possible to define figures of merit which a nonlinear material must satisfy in order for it to be useful for all-optical switching in waveguides (as well as other nonlinear devices). Here we first discuss the physical basis for these figures of merit. Examples of materials in which these figures of merit both are and are not satisfied will be given. Finally the evolution of nonlinear directional couplers will be reviewed and the impact of figures of merit identified.
TL;DR: In this paper, a DPP design for inertial-confinement-fusion (ICF) laser systems, used to irradiate fuel capsules, is presented, which exhibits near-unity energy efficiency, envelope and power spectrum flexibility, and reduced near field intensity modulation.
Abstract: Efficient phase conversion of laser light can be achieved using continuous distributed phase plates (DPPs) for applications in laser-beam shaping and laser-beam smoothing. These DPPs are deep, surface-relief, continuous phase plates that exhibit near-unity energy efficiency, envelope and power spectrum flexibility, and reduced near-field intensity modulation as compared to stepped diffractive optics. Specific DPP designs for inertial-confinement-fusion laser systems, used to irradiate fuel capsules, is presented.
TL;DR: In this article, an intensity modulated optical spectrometer (IMOS) is described, which uses four different wavelengths, a wideband modulation frequency (1 MHz to 500 MHz), and simultaneous measurement of three parameters the dc intensity, ac amplitude, and the phase shift.
Abstract: Quantitative determination of chromophore concentrations by near infrared spectroscopy (NIRS) is possible by using the differential pathlength of the detected light, measured noninvasively as the mean time delay of the impulse response function of the tissue. Experimentally this information in the time domain is also available in the frequency domain by intensity modulating the input light and sweeping the modulation frequency between zero and infinity. We describe an intensity modulated optical spectrometer which differs from previously described systems in using four different wavelengths, a wideband modulation frequency (1 MHz to 500 MHz), and the simultaneous measurement of three parameters the dc intensity, ac amplitude, and the phase shift. The measured dc intensity in conjunction with the ac phase shift data allows changes in absorption coefficient (and hence chromophore concentration) to be determined more accurately by correcting for real time path length variations. The ac phase shift in combination with the ac modulation depth theoretically allows for the absolute measurement of tissue absorption and scattering coefficient. Preliminary performance figures for the system suggest values of rms noise of 0.0006 OD, 0.0011 rad and 0.0008% for the measured attenuation, ac phase shift and modulation depth. Using a phantom of fixed geometry with known scattering and absorption properties, the ability of the system to reproduce the information content of the impulse response function for a homogeneous phantom is investigated.
TL;DR: In this paper, the birefringence loss in rat skin collagen heated in vitro was measured and the model coefficients were derived from exposure times between 600 and 6000s over the temperature range 45 to 90 degree(s)C.
Abstract: Thermal fusion or welding of collagen-rich tissues involves the thermal denaturation of collagen which is reflected by changes in birefringence intensity in histologic sections. The weld bond between two severed edges is formed when the apposed ends of the collagen fibrils unravel during heating then re-entwine during the cooling phase. Thermal coagulation of collagen can be described as an end point of a kinetic rate process of thermal damage which is linear with time of exposure and exponential with temperature. The kinetic rate coefficients, A (s-1) and E (J/mole), have been experimentally determined for birefringence loss in rat skin collagen heated in vitro -- A equals 1.606 X 1045 and E equals 3.06 X 105. Loss in collagen birefringence is a rare quantitative indicator of thermal damage; in this case, the structural alteration in tissue native-form collagen. The kinetic model coefficients were derived from exposure times between 600 and 6000s over the temperature range 45 to 90 degree(s)C. Room temperature control specimens were also analyzed for comparison.
TL;DR: The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) as discussed by the authors is a multi-spectral imaging radiometer with 14 spectral bands that will be launched in 1998 on NASA's EOS-AM1 platform.
Abstract: The advanced spaceborne thermal emission and reflection radiometer (ASTER), a multi- spectral imaging radiometer with 14 spectral bands, is a research facility instrument that will be launched in 1998 on NASA's EOS-AM1 platform. Characteristics of the ASTER data can be summarized as (1) wide spectral coverage from the visible to thermal infrared regions, (2) multispectral thermal infrared data with high spectral and spatial resolution and (3) stereoscopic capability in the along track direction. ASTER is currently being designed to meet the requirements given by the ASTER science team.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the SPOT-1 and -2 Haute Resolution Visible (HRV) cameras at White Sands, New Mexico were compared with the on-board tungsten lamp.
Abstract: Since their launch in February 1986 and January 1990, we have, from time to time, conducted radiometric calibrations of the SPOT-1 and -2 Haute Resolution Visible (HRV) cameras at White Sands, New Mexico. We summarize the results of the calibrations, comparing the absolute calibration coefficients obtained from the White Sands data to the relative calibrations obtained from the on-board tungsten lamp.