Time gate, optical layout, and wavelength effects on ballistic imaging

Idlahcen, Saïd; Méès, Loïc; Rozé, C; Girasole, Thierry; Blaisot, Jean‐Bernard

doi:10.1364/josaa.26.001995

Cited by 27 publications

(19 citation statements)

References 13 publications

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“…Although the detection system's depth of sharpness range is limited (80 mm), still multiple scattering is an issue and the disturbing stray light makes the optical access of the inner spray structures difficult. Therefore, further spray analyses also with enhanced optical techniques such as ballistic imaging 33,34 or X-ray techniques 35 are necessary. Finally, the turbulent, cavitating nozzle flow is characterized by a CFD simulation.…”

mentioning

confidence: 99%

Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector

Zigan

Shi

Krotow

et al. 2013

International Journal of Engine Research

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The effect of fuel properties and fuel temperature on the behaviour of the internal nozzle flow, atomization and cyclic spray fluctuations is examined for a three-hole direct injection spark ignition injector by combining numerical simulation of the nozzle flow with macroscopic and microscopic spray visualization techniques. A dominant influence of the liquid fuel viscosity on the highly unsteady, cavitating nozzle flow and spray formation was observed. A reduced viscosity (or larger Reynolds number) increases the flow velocity, turbulence and cavitation in the nozzle and leads to a slim spray with a reduced width but increased spray penetration. Furthermore, the spray cone angle is larger for lower Reynolds numbers due to the changed internal nozzle flow profile as predicted by the numerical calculation. The shot-to-shot fluctuations of the sprays were found to have their origin in the highly unsteady, cavitating nozzle flow. Larger cyclic spray fluctuations were observed at low Reynolds numbers although the predicted vapour formation in the nozzle is weaker. This can be explained by flow instabilities at low Reynolds numbers leading to large fluctuations in the nozzle flow.

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mentioning

confidence: 99%

Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector

Zigan

Shi

Krotow

et al. 2013

International Journal of Engine Research

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“…Most of the OKE time-gated imaging setups discussed in the literature employ a crossedbeam geometry in order to spatially separate the pump and image light [13][14][15][16]. The spatial overlap of the pump beam on the probe beam covers an area inside the Kerr medium corresponding to a constant time.…”

Section: Collinear Oke Time-gatingmentioning

confidence: 99%

“…A more detailed discussion on the use of two wavelengths in optical gating may be found in ref. [16]. Figure 6 shows that a cell thickness of 1.0 mm is a good compromise: it gives a temporal resolution of 1.04 ps (full width at half maximum) and allows one to recover the relaxation time of CS 2 .…”

Section: < V Pump Gmentioning

confidence: 99%

Collinear, two-color optical Kerr effect shutter for ultrafast time-resolved imaging

Purwar¹,

Idlahcen²,

Rozé³

et al. 2014

Opt. Express

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Imaging with ultrashort exposure times is generally achieved with a crossed-beam geometry. In the usual arrangement, an off-axis gating pulse induces birefringence in a medium exhibiting a strong Kerr response (commonly carbon disulfide) which is followed by a polarizer aligned to fully attenuate the on-axis imaging beam. By properly timing the gate pulse, imaging light experiences a polarization change allowing time-dependent transmission through the polarizer to form an ultrashort image. The crossed-beam system is effective in generating short gate times, however, signal transmission through the system is complicated by the crossing angle of the gate and imaging beams. This work presents a robust ultrafast time-gated imaging scheme based on a combination of type-I frequency doubling and a collinear optical arrangement in carbon disulfide. We discuss spatial effects arising from crossed-beam Kerr gating, and examine the imaging spatial resolution and transmission timing affected by collinear activation of the Kerr medium, which eliminates crossing angle spatial effects and produces gate times on the order of 1 ps. In addition, the collinear, two-color system is applied to image structure in an optical fiber and a gasoline fuel spray, in order to demonstrate image formation utilizing ballistic or refracted light, selected on the basis of its transmission time. 16, 1868-1870 (1991). 9. K. M. Yoo, Q. Xing, and R. R. Alfano, "Imaging objects hidden in highly scattering media using femtosecond second-harmonic-generation cross-correlation time gating," Opt. Lett. 16, 1019Lett. 16, -1021Lett. 16, (1991. 10. S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, "Sub-picosecond ballistic imaging of a liquid jet,"Exp. Fluids 52, 289-298 (2011). 11. L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, "Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate," Science 253, 769-771 (1991). 12. R. Alfano, ed., Semiconductors probed by ultrafast laser spectroscopy (Academic, 1984, vol. II

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“…More in-depth discussions of the quantitative relation of these parameters can be found in [62, 65, 66, 67, 68, 69, 70]. A special case of the temporal modulation methods is the so-called early photon (also known as ballistic photon) imaging method, which uses ultrafast laser and detector time-gating to reduce the TPSF of the imaging system, thereby improving the spatial resolution [71, 72, 73]. …”

Section: Signal Modulationmentioning

confidence: 99%

Instrumentation in Diffuse Optical Imaging

Zhang

2014

Photonics

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Diffuse optical imaging is highly versatile and has a very broad range of applications in biology and medicine. It covers diffuse optical tomography, fluorescence diffuse optical tomography, bioluminescence, and a number of other new imaging methods. These methods of diffuse optical imaging have diversified instrument configurations but share the same core physical principle – light propagation in highly diffusive media, i.e., the biological tissue. In this review, the author summarizes the latest development in instrumentation and methodology available to diffuse optical imaging in terms of system architecture, light source, photo-detection, spectral separation, signal modulation, and lastly imaging contrast.

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Time gate, optical layout, and wavelength effects on ballistic imaging

Cited by 27 publications

References 13 publications

Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector

Fuel property and fuel temperature effects on internal nozzle flow, atomization and cyclic spray fluctuations of a direct injection spark ignition–injector

Collinear, two-color optical Kerr effect shutter for ultrafast time-resolved imaging

Instrumentation in Diffuse Optical Imaging

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