High Speed Photography of Fast Moving Particles

Abstract

A system of high speed photography has been designed in order to measure the size and velocity of particles whose diameters lie between 10 and 100 microns, and whose velocities lie within the range of 500 to 1,000 ft./sec. The principle employed is that of “panning”, at known speed, the magnified optical image of 0 moving porticle by means of an image converter tube, so that the electron image is held stationary on the screen phosphor while the actual particle moves across the illuminated field of view. Under these conditions, the exposure time con be mode some thousand times greater than that required to toke a “still” photograph of the original particle. Problems of adequately illuminating the particle during the longer period of exposure are correspondingly reduced, whilst picture quality is increased. In order to ensure that each photographic record contains on adequate number of images for ease of analysis. multiple Exposures are made on a single film Frome. In order to prevent inevitable degradation of each image by over-exposure, an inverted stage is included in the photographic system so that the sequence of exposures made in the camera results in a number of white images on a dark background. Apart from the necessary electronic supplies and controls, the system consists essentially of a repetitive spark-discharge light source, a long working-distance optical system, an image converter tube, a vidicon camera channel with display monitors, and a photographic camera

Notes

Paper presented at the Spring. Conference of the British National ol1lmillee for High Speed I’holography held at Leeds University, 18 19 April 1966.

Present address; Deparll’nenl of Chemical Engineering, Houldsworth School of Applied Science. The University, Leeds. 2.