Preliminary Development of a Nearly-Instantaneous Three- Dimensional Imaging Technique for High-Speed Flow Fields

Recent advances in high-repetition rate laser and camera technology present a new opportunity to develop three-dimensional diagnostics for high-speed flows. The design of a three-dimensional imaging system based on a pulse burst laser, a high-speed laser scanner and a high speed camera is described here. The pulse burst laser system is the 5 th of its kind in the world and can produce high energy pulses at up to 10 MHz repetition rates. A highspeed optical deflector, such as a rotating mirror or acousto-optic deflector, can be used to rapidly deflect a laser sheet through the flow field. A high-speed camera can then be used to collect images at different planes in the flow field, from which a three-dimensional image can be reconstructed. The state-of-the-art of these technologies are described. The high-speed characteristics of an acousto-optic deflector were tested using an Nd:YAG laser where it was found that a full sweep through at least 32 resolvable spots could be completed in 10 μsec. Future work will include testing of a galvanometric scanning mirror and assembly of a complete system.

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