Key techniques of high-speed photomicrography in ship wake research

Aiming at the little bubbles with about 10 um diameters in ship wake research, a new method to obtain the dimension, number density and retention time of these bubbles by underwater high-speed photomicrography technique was introduced. The underwater photomicrography optical system against little bubbles was analyzed. The key techniques such as depth of field, lighting, etc. were discussed. The main technical parameters of system were ascertained. The underwater high-speed photomicrography can be realized only when frame rate is 500 fps, picture element is 10 × 10 um2, the least exposure time is 1 μs, optical system magnification is 3 times, focus is 75 mm, and relative apertures are adjustable. The depth of field and lighting was specially designed.