Intensified Charge-coupled Device Research Articles

Concentration of Indocyanine Green Does Not Significantly Influence Lymphatic Function as Assessed by Near-Infrared Imaging

Absorbance of near-infrared (600-800 nm) light by the tissue components water, melanin, and hemoglobin is minimal. This property allows the use of near-infrared-emitting fluorophores for noninvasive, in vivo, real-time imaging of tissue, without the interference of autofluorescence experienced with imaging in other wavelength ranges. Near-infrared (NIR) fluorescence imaging has been used to noninvasively image lymphatic architecture and pumping function in animals, as well as in humans. The effects of different doses of a NIR dye, indocyanine green (ICG), on lymphatic function have been questioned. This study aims to address these concerns in the context of a mouse inguinal-to-axillary lymphatic imaging model. We measured lymph propulsive velocity and frequency using an imaging system composed of a laser diode for excitation of the dye, an image intensifier, and an intensified charge-coupled device (ICCD) camera to capture real-time images. At 0.32, 0.645, and 1.3 mM ICG, no significant differences in lymphatic propulsive velocity or frequency were observed. Additionally, the use of other NIR imaging agents did not result in significant differences. The use of different concentrations of ICG and the use of other near-infrared fluorophores for optical imaging of lymphatics does not significantly affect lymphatic propulsive velocity or frequency.

Optical diagnosis and theoretical simulation of laser induced lead plasma spectrum

Plasmas generated during incipient laser ablation of lead in air were studied using emission spectroscopy and fast photography by an intensified charge coupled device (ICCD) camera. An improved plasma emission model was introduced, invoking one-dimensional radiative transfer, to describe the observed emission spectra, while taking into account Gaussian intensity distribution of the laser used to form plasma. The effects of different parameters to the fitting results are discussed. The plasma temperature got by Saha-Boltzmann plot method and the electron number density got by line broadening method were compared with the fitting results. We also found that the distribution of plasma temperature is more uniform than that of the electron number density in the radial direction.

Three-step nonuniformity correction for a highly dynamic intensified charge-coupled device star sensor

A three-step nonuniformity correction algorithm based on the photoelectrical response models of intensified charge-coupled device (ICCD) for a highly dynamic ICCD star sensor is proposed in the current paper. The influence factors of nonuniformity correction precision are analyzed based on the photoelectrical imaging theory. The photoelectrical response models of ICCD are obtained using the experimental method, and the nonuniformity correction is implemented in three steps based on the photoelectrical response models. The nonuniformity correction results in constant-radiance images and sky images of the highly dynamic star sensor show that the proposed algorithm has satisfactory correction precision, and the accuracy of the highly dynamic star sensor can be enhanced effectively when sky images are processed using the three-step nonuniformity correction algorithm.

Comparison research on the laser plasma spectra with and without obvious self-absorption

Characteristics of laser produced Pb plasma were investigated using the spectrograph and the fast photography by an intensified charge coupled device (ICCD) camera. The optical emission spectra and images of the plasma were recorded and analyzed. The clear self-reversed structure can be revealed in the emission spectra of the lead plasma when the target is at 6 mm before the focus of lens. However, the self- absorption can not be observed in the spectra if the target is located at the focus. The electron temperature, the electron number density and the lower level atomic number density were obtained by fitting the experimental spectra at different delay times under the two circumstances. The electron number density and the lower level atomic number density are higher, as the target is at 6 mm before the focus of lens, however the electron temperature is lower as the target is located at the focus, under the same laser energy.

Stand-Off Spatial Offset Raman Spectroscopy for the Detection of Concealed Content in Distant Objects

A pulsed (4.4 ns pulse length) frequency-doubled Nd:YAG laser operated at 10 Hz was used to generate Raman scattering of samples at a distance of 12 m. The scattered light was collected by a 6 in. telescope, and the Raman spectrum was recorded using an Acton SP-2750 spectrograph coupled to a gated intensified charge-coupled device (ICCD) detector. Applying a spatial offset between the point where the laser hit the sample and the focus of the telescope on the sample enabled collection of Raman photons that were predominantly generated inside the sample and not from its surface. This is especially effective when the content of concealed objects should be analyzed. High-quality Raman spectra could be recorded, within 10 s of data acquisition, from a solid (NaClO(3)) as well as a liquid (isopropyl alcohol) placed inside a 1.5 mm thick opaque low-density polyethylene (LDPE) plastic bottle. The applied spatial offset was also advantageous in cases where the surface of the container was highly fluorescent. In such a situation, Raman spectra of the sample could not be recorded when the sampling volume (telescope observation field) coincided with the focus of the excitation laser. However, with the use of a spatial offset of some millimeters, a clear Raman spectrum of the content (isopropyl alcohol) in a strongly fluorescent plastic container was obtained.

Three-Dimensional ICCD Observation of Dual Sustain Discharge Mode in Three-Electrode Microdischarge Cell

The spatiotemporal variations in a 3-D discharge cell are measured using infrared emission images taken with an intensified charge-coupled device (ICCD) camera. The 3-D ICCD analysis of the discharges from the conventional single surface discharge mode and a new dual surface discharge mode revealed that the discharge from the dual surface discharge mode spread toward the MgO layer in the front panel, thereby avoiding the impingement of energetic ions into the phosphor layer.

Self-Organization Pattern of Microgap Atmospheric Barrier Discharge

Symmetric self-organized discharge filaments have been observed in the 140- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $\mu\hbox{m}$</tex></formula> -microgap dielectric barrier discharge between two parallel glass plates. Images of the discharge in microseconds were obtained using an intensified charge-coupled device (ICCD) camera. The diameters of these self-organizing filaments, the distance between the filaments, and the approximate speed of the moving filaments were obtained using the ICCD images.

Temporally Resolved Imaging of Jet-Type Dielectric Barrier Discharge Using He and Ar/Acetone Crossed Gas Flows

We report on temporally resolved images in a jet-type dielectric barrier discharge with two crossed gas flows obtained by a spectrally filtered intensified charge-coupled device (ICCD) camera. The crossed-flow configuration of He and Ar gases and a small acetone impurity added into the Ar flow simulated a discharge configuration and an organic precursor used for the practical application of material processing, respectively. From the ICCD images, streamer and transient glow discharges could be distinguished between the electrode and the substrate. Filtered emission from excited N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , CH, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , He, and Ar also revealed the excitation and decomposition processes in the discharge.

Noninvasive Detection of Concealed Explosives: Depth Profiling through Opaque Plastics by Time-Resolved Raman Spectroscopy

The detection of explosives concealed behind opaque, diffusely scattering materials is a challenge that requires noninvasive analytical techniques for identification without having to manipulate the package. In this context, this study focuses on the application of time-resolved Raman spectroscopy (TRRS) with a picosecond pulsed laser and an intensified charge-coupled device (ICCD) detector for the noninvasive identification of explosive materials through several millimeters of opaque polymers or plastic packaging materials. By means of a short (250 ps) gate which can be delayed several hundred picoseconds after the laser pulse, the ICCD detector allows for the temporal discrimination between photons from the surface of a sample and those from deeper layers. TRRS was applied for the detection of the two main isomers of dinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene as well as for various other components of explosive mixtures, including akardite II, diphenylamine, and ethyl centralite. Spectra were obtained through different diffuse scattering white polymer materials: polytetrafluoroethylene (PTFE), polyoxymethylene (POM), and polyethylene (PE). Common packaging materials of various thicknesses were also selected, including polystyrene (PS) and polyvinyl chloride (PVC). With the demonstration of the ability to detect concealed, explosives-related compounds through an opaque first layer, this study may have important applications in the security and forensic fields.

Stand-off detection of explosives particles by multispectral imaging Raman spectroscopy

A Raman multispectral imaging technique is presented, which can be used for stand-off detection of single explosives particles. A frequency-doubled Nd:YAG laser operating at 10 Hz illuminates the surface under investigation. The backscattered Raman signal is collected by a receiver subsystem consisting of a 150 mm Schmidt-Cassegrain telescope, a laser line edge filter, a liquid-crystal tunable filter, and a gated intensified charge-coupled device (ICCD) detector. A sequence of images is recorded by the ICCD, where, for each recording, a different wavelength is selected by the tunable filter. By this, a Raman spectrum is recorded for each pixel, which makes it possible to detect even single particles when compared to known spectra for possible explosives. The comparison is made using correlation and least-square fitting. The system is relatively insensitive to environment and light variations. Multispectral Raman images of sulfur, ammonium nitrate, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene were acquired at a stand-off distance of 10 m. Detection of sulfur particles was done at a distance of 10 m.

A quantitative analysis of elements in soil using laser-induced breakdown spectroscopy technique

Laser-induced breakdown spectroscopy (LIBS) was applied to the quantitative analysis of elemental composition of soil. The experiment was performed in air at atmospheric pressure and at room temperature. A Nd:YAG laser with the fundamental wavelength of 1064 nm was employed to generate the soil plasma. The emission spectra from the plasma were collected by the Cerny-Turner type of spectrometer, which was equipped with an intensified charge-coupled device (ICCD). The plasma temperature and electron density were evaluated by the Boltzmann plot method and the Saha-Boltzmann equation respectively. Then the concentrations of elements in soil were further obtained by the internal standard of iron element and some selected atomic/ionic lines. In order to prove the credibility and reliability of the present LIBS results, a comparison between the LIBS results and the nominal concentrations was performed. It was found that the LIBS results agree with the nominal concentrations. Therefore the LIBS technique promises to fast and in simultaneous multi-element quantitative analysis of soil.

The influence of plasma dynamics on the growth of Sm 0.55Nd 0.45NiO 3 solid solution during pulsed laser deposition

We report on the presence of an interesting cross-correlation among the deposition parameters, which are usually overlooked in the usual empirical approach used by pulsed laser deposition growers. The fast intensified-charge-coupled-device (ICCD) photography imaging studies of the plasma generated by the KrF excimer laser ablation of Sm 1− x Nd x NiO 3 at x=0.45 in the presence of oxygen background gases at different pressures is reported. The experimentally determined behaviours are compared with the predictions of an analytical model, which gives a complete description of the expansion of the plume and with some recent results reported in the literature. Evidence of the strong influence of the expansion plasma regime was found, which showed that it is not simply related to the overall reactive gas content. Our findings demonstrate that the optimisation of the pulsed laser deposition parameters, such as gas pressure, should be performed also taking into account the chemical pressure induced by the substrate nature. The analysis of the experimental results allowed us to estimate the average deposition oxygen pressure for Sm 0.55Nd 0.45NiO 3 in the typical range used for Pulsed Laser Deposition (PLD) of complex oxides, showing that the higher the deposition pressure, the better the crystallinity.

Spatial distribution of sonoluminescence and sonochemiluminescence generated by cavitation bubbles in 1.2 MHz focused ultrasound field

An intensified charge coupled device (ICCD) camera was used to observe the spatial distribution of sonoluminescence (SL) and sonochemiluminescence (SCL) generated by cavitation bubbles in a 1.2 MHz focused ultrasound (FU) field in order to investigate the mechanisms of acoustic cavitation under different sonication conditions for FU therapeutic applications. It was found that SL emissions were located in the post-focal region. When the intensity of SL and SCL increased as the power rose, the growth of SCL was much higher than that of SL. In the post-focal region, the SCL emissions moved along specific paths and formed branch-like streamers. At the beginning of the ultrasound irradiation, cavitation bubbles generated SCL in both the pre-focal and the post-focal region. When the electrical power or the sonication time increased, the SCL in the post-focal region increased and became higher than that in the pre-focal region. The intensity of SCL in the focal region is usually the weakest because of “oversaturation”. The spatial distribution of SCL near a tissue boundary differed from that obtained in free fields. It organized into special structures under different acoustic amplitudes. When the electrical power was relatively low, the SCL emission was conical shape which suggested a standing wave formation at the tissue–fluid boundary. When the electrical power exceeded a certain threshold, only a bright spot could be captured in the focus. The cavitation bubbles which centralized in the focus concentrated energy and hindered the formation of standing waves. With rising electrical power at high levels, besides a bright spot in the focus, there were some irregular light spots in pre-focal region, which indicated some cavitation bubbles or small bubble clusters achieved the threshold of SCL and induced the reaction with the luminol solution.

Discrimination of organic solid materials by LIBS using methods of correlation and normalized coordinates

The methods of linear and rank correlation and normalized coordinates (MNC) have been applied to the identification of organic solid materials with a very similar chemical composition by laser-induced breakdown spectroscopy (LIBS). The present study evaluated these three statistical methods using an Echelle spectrometer coupled with an intensified charge-coupled device (ICCD). Moreover, three instrumental parameters (laser pulse energy, delay time and integration time) were evaluated in terms of their influence on the signal-to-noise ratio of carbon and hydrogen emission lines. The probability of a right identification can be estimated by means the described methods in this paper. Methods of correlation provide better identification and discrimination than normalized coordinates at a 95% confidence level.

Coaxial rf atmospheric pressure dielectric barrier air–helium plasma characteristics

The electrical and optical characteristics of a coaxial rf atmospheric pressure dielectric barrier discharge (DBD) with one electrode covered with glass and with helium in air were investigated. Optical measurements with an intensified charge coupled device (ICCD) camera combined with the voltage and power vs. current data provided identification of the α to γ mode transitions. The coaxial design allowed operation with very low power density plasmas (0.18 W/cm3) and a much larger plasma size (13 mm) than the parallel plate designs.

Thermometry in noble gas dielectric barrier discharges at atmospheric pressure using optical emission spectroscopy

We measure the temperature, T, of dielectric barrier discharges (DBD), in noble gases using optical emission spectroscopy (OES), by analysing rotational bands in the emission spectra of the first negative system (FNS) of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> . This has the advantage that rotational structure can be fully resolved even with a spectrograph of average performance, and that the rotational temperature, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rot</sub> (~ T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gas</sub> ) can then be determined from a conventional Boltzmann plot. Ionization of N2 occurs mainly via Penning transfer from metastable excited states of He (ca. 20 eV) or Ne (ca. 16.6 eV). Using two glass-walled DBD chambers of very different volumes (0.1 and 20 liters), we have studied atmospheric-pressure discharges in flowing helium (He) or neon (Ne) containing traces of nitrogen. Discharges were excited by audio-frequency (10 kHz) high voltage (HV) using a needle as the HV electrode and a dielectric (alumina)-covered planar grounded counter-electrode. OE spectra were acquired with a 0.5 m focal length spectrograph, coupled to an intensified charge coupled device (ICCD) detector. Using the (0-0) R-branch of the FNS N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> (B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> - X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) bands near a wavelength of 391.4 nm, we have measured axial (inter-electrode) distributions of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rot</sub> for the two different reactor volumes in both He and Ne. T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rot</sub> values were found to be highest at the needle electrode, of about 450 K and 740 K for He and Ne, respectively; in He, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rot</sub> dropped to a minimum of about 405 K at the mid-gap position in the small chamber, and ~ 360 K near the planar electrode in the large chamber. We conclude that temperatures in noble gas discharges depend critically on thermal conductivities of the particular gases (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">He</sub> = 1.9; K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ne</sub> = 0.6, both in mW.cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> .K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) and on other experimental factors that influence heat transfer.

Spectroscopy of laser-produced plasmas: Setting up of high-performance laser-induced breakdown spectroscopy system

It is a well-known fact that laser-induced breakdown spectroscopy (LIBS) has emerged as one of the best analytical techniques for multi-elemental compositional analysis of samples. We report assembling and optimization of LIBS set up using high resolution and broad-range echelle spectrograph coupled to an intensified charge coupled device (ICCD) to detect and quantify trace elements in environmental and clinical samples. Effects of variations of experimental parameters on spectroscopy signals of copper and brass are reported. Preliminary results of some plasma diagnostic calculations using recorded time-resolved optical emission signals are also reported for brass samples.

Physical mechanism of silicon ablation with long nanosecond laser pulses at 1064 nm through time-resolved observation

Nanosecond (ns) laser ablation can provide a competitive solution for silicon micromachining in many applications. However, most of the previous studies focus on ns lasers at visible or ultraviolet (UV) wavelengths. The research is very limited for ns lasers at infrared (e.g., 1064nm) wavelengths (which often have the advantage of much lower cost per unit average output power), and the research is even less if the ns laser also has a long pulse duration on the order of ∼100ns. In this paper, time-resolved observation using an ICCD (intensified charge-coupled device) camera has been performed to understand the physical mechanism of silicon ablation by 200-ns and 1064-nm laser pulses. This kind of work has been rarely reported in the literature. The research shows that for the studied conditions, material removal in laser silicon ablation is realized through surface vaporization followed by liquid ejection that occurs at a delay time of around 200–300ns. The propagation speed is on the order of ∼1000m/s for laser-induced plasma (ionized vapor) front, while it is on the order of ∼100m/s or smaller for the front of ejected liquid. It has also been found that the liquid ejection is very unlikely due to phase explosion, and its exact underlying physical mechanism requires further investigations.

Time‐resolved microscopy for imaging lanthanide luminescence in living cells

Time-resolved luminescence (TRL) microscopy can image signals from lanthanide coordination complexes or other probes with long emission lifetimes, thereby eliminating short-lifetime (<100 ns) autofluorescence background from biological specimens. However, lanthanide complexes emit far fewer photons per unit time than conventional fluorescent probes, making it difficult to rapidly acquire high quality images at probe concentrations that are relevant to live cell experiments. This article describes the development and characterization of a TRL microscope that employs a light-emitting diode (LED, λ(em) = 365 nm) for pulsed epi-illumination and an intensified charge-coupled device (ICCD) camera for gated, widefield detection. Europium chelate-impregnated microspheres were used to evaluate instrument performance in terms of short-lifetime fluorescence background rejection, photon collection efficiency, image contrast, and signal-to-noise ratio (SNR). About 200 nm microspheres were imaged within the time resolution limit of the ICCD (66.7 ms) with complete autofluorescence suppression. About 40 nm microspheres containing ~400 chelate molecules were detected within ~1-s acquisition times. A luminescent terbium complex, Lumi4-Tb®, was introduced into the cytoplasm of cultured cells at an estimated concentration of 300 nM by the method of osmotic lysis of pinocytic vesicles. Time-resolved images of the living, terbium complex-loaded cells were acquired within acquisition times as short as 333 ms, and the effects of increased exposure time and frame summing on image contrast and SNR were evaluated. The performance analyses show that TRL microscopy is sufficiently sensitive and precise to allow high-resolution, quantitative imaging of lanthanide luminescence in living cells under physiologically relevant experimental conditions.

Effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 μm, 30 J pulse energy was used to ablate water contained in a quadrate quartz container. Net imparted impulse and coupling coefficients were derived from the force sensor data and relevant results were presented for various laser energy densities. ICCD imaging was used in conjunction with the dynamic force techniques to examine the dependencies on laser energy density. Results showed that the impulse coupling coefficient could reach a maximum value when laser energy density was about 105 J/m2, and it would increase before laser energy got to this point and would decrease after this point, and ICCD imaging supplied important phenomenon to explain this variation, which were water ablation before laser energy density got to 105 J/m2 and laser-induced air-breakdown with water as an induction when laser energy density was higher than 105 J/m2.