Single-laser shot fluorescence lifetime imaging on the nanosecond timescale using a Dual Image and Modeling Evaluation algorithm

Ehn, Andreas; Johansson, Olof; Arvidsson, Åke; Aldén, Marcus; Bood, Joakim

doi:10.1364/oe.20.003043

Cited by 23 publications

(15 citation statements)

References 29 publications

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“…It is essential that both cameras capture different temporal information from the LII decay so that the ratio of both signals is a sensitive measure of the decay. Both images can be acquired either with various delays [9,25] and/or gate widths [26,27] within the signal decay. For each combination of delays and gate widths, signals and signal ratios can be computed by convoluting the temporal characteristics of the detectors with the respective LII signal library.…”

Section: Particle-size Imagingmentioning

confidence: 99%

Assessment of soot particle-size imaging with LII at Diesel engine conditions

et al. 2015

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International audienceTwo-time-step laser-induced incandescence (LII) imaging was performed in Diesel engine-relevant combustion to investigate its applicability for spatially-resolved measurements of soot primary particle sizes. The method is based on evaluating gated LII signals acquired with two cameras consecutively after the laser pulse and using LII modeling to deduce the particle size from the ratio of local signals. Based on a theoretical analysis, optimized detection times and durations were chosen to minimize measurement uncertainties. Experiments were conducted in a high-temperature high-pressure constant-volume pre-combustion vessel under the Engine Combustion Network's (ECN) "Spray A" conditions at 61–68 bar with additional parametric variations of injection pressure, gas temperature, and composition. The LII measurements were supported by pyrometric imaging measurements of particle heat-up temperatures. The results were compared to particle-size and size-dispersion measurements from transmission electron microscopy (TEM) of soot thermophoretically sampled at multiple axial distances from the injector. The discrepancies between the two measurement techniques are discussed to analyze uncertainties and related error sources of the two diagnostics. It is found that in such environment where particles are small and pressure is high, LII signal decay times are such that LII with standard nanosecond laser and detector equipment suffers from a strong bias towards large particles

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Section: Particle-size Imagingmentioning

confidence: 99%

Assessment of soot particle-size imaging with LII at Diesel engine conditions

et al. 2015

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“…The simple yet unique ability of FRAME to acquire several laser images in one recording also enables new measurement opportunities. For example, combining FRAME with currently existing laser methods for fluorescence lifetime imaging 28 (FLI) of single events 29 would allow all FLI data to be collected in one image recording. Finally, the ultimate purpose of single-event videography is to use the existing knowledge of ultrafast dynamics gained from studies of reduced systems to understand evolving global systems; we believe FRAME can facilitate achievement of this endeavor.…”

Section: Discussionmentioning

confidence: 99%

FRAME: femtosecond videography for atomic and molecular dynamics

et al. 2017

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Many important scientific questions in physics, chemistry and biology require effective methodologies to spectroscopically probe ultrafast intra- and inter-atomic/molecular dynamics. However, current methods that extend into the femtosecond regime are capable of only point measurements or single-snapshot visualizations and thus lack the capability to perform ultrafast spectroscopic videography of dynamic single events. Here we present a laser-probe-based method that enables two-dimensional videography at ultrafast timescales (femtosecond and shorter) of single, non-repetitive events. The method is based on superimposing a structural code onto the illumination to encrypt a single event, which is then deciphered in a post-processing step. This coding strategy enables laser probing with arbitrary wavelengths/bandwidths to collect signals with indiscriminate spectral information, thus allowing for ultrafast videography with full spectroscopic capability. To demonstrate the high temporal resolution of our method, we present videography of light propagation with record high 200 femtosecond temporal resolution. The method is widely applicable for studying a multitude of dynamical processes in physics, chemistry and biology over a wide range of time scales. Because the minimum frame separation (temporal resolution) is dictated by only the laser pulse duration, attosecond-laser technology may further increase video rates by several orders of magnitude.

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“…0-0 and 1-1 obviously needs to be distinguished, which can be done using a spectral filter with a very sharp transmission edge at 312 nm. However, it is also possible to extract 24,25 is implemented in a setup based on picosecond laser excitation. Whether an approach based on the spectral band intensity ratio would be better than the temporal approach is essentially a question about which filter is the sharpest, i.e.…”

Section: Demonstration Of 2-d Imagingmentioning

confidence: 99%

“…With the camera gate functions thoroughly characterized, these functions can be included in the model, allowing quantification of the H 2 O concentration without calibration. In addition optimum gate timings can be determined more accurately from modeling results, as described in Ref 24…”

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confidence: 99%

Simultaneous Visualization of Hydrogen Peroxide and Water Concentrations Using Photofragmentation Laser-Induced Fluorescence

2017

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A concept based on photofragmentation laser-induced fluorescence (PFLIF) is for the first time demonstrated for simultaneous detection of hydrogen peroxide (HO) and water (HO) vapor in various mixtures containing the two constituents in a bath of argon gas. A photolysis laser pulse at 248 nm dissociates HO into OH fragments, whereupon a probe pulse, delayed 100 ns and tuned to an absorption line in the AΣ (v = 1) ← XΠ(v = 0) band of OH near 282 nm, induces fluorescence. The total OH fluorescence reflects the HO concentration, while its spectral shape is utilized to determine the HO concentration via a model predicting the ratio between the fluorescence intensities of the AΣ (v = 1) → XΠ(v = 1) and the AΣ (v = 0) → XΠ(v = 0) bands. The HO detection scheme requires that the bath gas has a collisional cross-section with OH(A) that is significantly lower than that of HO, which is the case for argon. Spectrally dispersed OH fluorescence spectra were recorded for five different HO/HO/Ar mixtures; the HO concentration in the range of 30-500 ppm and the HO concentration in the range of 0-3%. Fluorescence intensity ratios predicted by the model for these mixtures agree very well with corresponding experimental data, which thus validates the model. The concept was also demonstrated for two-dimensional imaging, using two intensified charge-coupled device (CCD) cameras for signal detection. Water content was here sensed through the different temporal characteristics of the two fluorescence bands by triggering the two cameras so that one captures the total OH fluorescence while the other one captures only the early part, which mainly stems from AΣ (v = 1) → XΠ(v = 1) fluorescence. Hence, the HO concentration is reflected by the image of the camera recording the total OH fluorescence, whereas HO concentration is extracted from the ratio between the two camera images. Quantification of the concentrations was carried out based on calibration measurements performed in known mixtures of HO (30-500 ppm) and HO (0-3%) in bulk argon. The detection limits for single-shot imaging are estimated to be 20 ppm for HO and 0.05% for HO. The authors believe that the concept provides a valuable asset in, for example, pharmaceutical or aseptic food packaging applications, where HO/HO vapor is routinely used for sterilization.

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Single-laser shot fluorescence lifetime imaging on the nanosecond timescale using a Dual Image and Modeling Evaluation algorithm

Cited by 23 publications

References 29 publications

Assessment of soot particle-size imaging with LII at Diesel engine conditions

Assessment of soot particle-size imaging with LII at Diesel engine conditions

FRAME: femtosecond videography for atomic and molecular dynamics

Simultaneous Visualization of Hydrogen Peroxide and Water Concentrations Using Photofragmentation Laser-Induced Fluorescence

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