Abstract: A laser system having a laser rod, flash lamp, and a Q-switch including an electro-optical cell, is operated to provide double laser output pulses closely spaced from each other, e.g., within 5 microseconds. Two Q-switch drivers are provided with independent high voltage power supplies which can provide different high voltages to the two Q-switches. The outputs of the Q-switches are provided to an interface circuit which includes back-to-back diodes connected to a node which is connected to the output provided to the electro-optical cell. A control signal is provided to the first Q-switch driver after the flash lamp has been fired to provide a first pulse to the electro-optical cell to provide a pulse of light from the laser. A selected period of time thereafter, a control signal is provided to the second Q-switch driver to provide an output pulse through the interface circuit to the electro-optical cell to provide the second light pulse from the laser.

Abstract: Young's fringes are produced from a double exposure image of particles in a flowing fluid by passing laser light through the film and projecting the light onto a screen. A video camera receives the image from the screen and controls a spatial light modulator. The spatial modulator has a two dimensional array of cells the transmissiveness of which are controlled in relation to the brightness of the corresponding pixel of the video camera image of the screen. A collimated beam of laser light is passed through the spatial light modulator to produce a diffraction pattern which is focused onto another video camera, with the output of the camera being digitized and provided to a microcomputer. The diffraction pattern formed when the laser light is passed through the spatial light modulator and is focused to a point corresponds to the two dimensional Fourier transform of the Young's fringe pattern projected onto the screen. The data obtained froThis invention was made with U.S.