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Ultra-high speed imaging in fluids by means of pulsed laser illumination at up to tens of MHz rates
The imaging of high-speed small-scale flow phenomena such as cavitation shock waves inception or microbubble ultrasound contrast agents dynamics require both a low exposure time and a high optical magnification and therefore extremely intense and short light pulses. In this project we aim to make use of lasers to create a sufficiently powerful and versatile illumination system for studying high-speed phenomena in fluids.
Revealing the nanosecond dynamics of micrometrical flow phenomena, such as microbubble ultrasound contrast agents oscillations, necessitates ultra-fast cameras with recording speed in the order of millions of frames-per-second and high-magnification microscopic system and, consequently, extremely high lighting power densities, motivating the use of lasers as light sources, which can be focused down to very small spot sizes.
Capturing sharp images of shock wave dynamics with continuous illumination is even more demanding, requiring few nanoseconds of exposure time with preferably a megapixel resolution or more. Despite the ongoing progress, high-speed cameras meeting these requirements are still far from being commercially available. An alternative approach is to capture the phenomenon of interest multiple times during a single exposure, where it is sufficient to use a simple high-resolution still camera with pulsed illumination. Again, to achieve ultra-short high-brightness pulses, lasers are essential.
Revealing the nanosecond dynamics of micrometrical flow phenomena, such as microbubble ultrasound contrast agents oscillations, necessitates ultra-fast cameras with recording speed in the order of millions of frames-per-second and high-magnification microscopic system and, consequently, extremely high lighting power densities, motivating the use of lasers as light sources, which can be focused down to very small spot sizes. Capturing sharp images of shock wave dynamics with continuous illumination is even more demanding, requiring few nanoseconds of exposure time with preferably a megapixel resolution or more. Despite the ongoing progress, high-speed cameras meeting these requirements are still far from being commercially available. An alternative approach is to capture the phenomenon of interest multiple times during a single exposure, where it is sufficient to use a simple high-resolution still camera with pulsed illumination. Again, to achieve ultra-short high-brightness pulses, lasers are essential.
The goal of this project is to upgrade an already existing and successful student-built speckle-free laser illumination system to allow the generation of fully user-customisable trains of pulses, in terms of pulse duration, interpulse time and pulse energy, synchronised with the camera. Our strategy is to use a high-performance laser driver to supply precisely modulated current at MHz rates to the laser diode to control its optical output.
This approach will be validated carrying out high-speed imaging experiments in fluids: cavitation shock wave velocimetry with a still camera for a multi-illumination-single-frame approach
and microbubble ultrasound-induced oscillations measurement with an ultra fast camera for a multi-illumination-multi-frame approach.
The goal of this project is to upgrade an already existing and successful student-built speckle-free laser illumination system to allow the generation of fully user-customisable trains of pulses, in terms of pulse duration, interpulse time and pulse energy, synchronised with the camera. Our strategy is to use a high-performance laser driver to supply precisely modulated current at MHz rates to the laser diode to control its optical output. This approach will be validated carrying out high-speed imaging experiments in fluids: cavitation shock wave velocimetry with a still camera for a multi-illumination-single-frame approach and microbubble ultrasound-induced oscillations measurement with an ultra fast camera for a multi-illumination-multi-frame approach.
For additional information, the candidates can contact Marco Cattaneo via email (mcattaneo at ethz.ch)
For additional information, the candidates can contact Marco Cattaneo via email (mcattaneo at ethz.ch)