Sub-Microsecond Electro-Optical Shutter

Abstract

The Directed Energy Group at BDM Albuquerque, under contract to the Directed Energy Directorate of the U.S. Army, MICOM, Redstone Arsenal, Huntsville, Alabama, has developed a concept to achieve an effective ten million frames-per-second infrared videograph for intensity distribution diagnostics of high power CO₂ laser pulses. The concept uses separate pyroelectric surfaces, either vidicons or self-scanning arrays, for each desired frame of data. The pyroelectric surface acts as analog storage of the image until such time as it can be digitized and read into data storage between laser pulses. Each pyro-electric surface is shuttered in sequence by Pockel's cells, with adjustable shutter "on" times and frame-to-frame timing as short as 100 nanoseconds. This paper constitutes a continuation of the design detail of the shutter and optical system for the IR video camera. A delay in the procurement provided time to rework the shutter design previously reported.¹ The revised design reduces the impractically high pulse currents by matching the high voltage pulse generator and line impedance to the Pockel's cell's impedance at the desired pulse rise time rather than the reverse, as in the original design. The optical design has been revised to incorporate a kinematic lens mount to facilitate the field replacement of the objective lenses necessitated by the two design applications. Both of these improvements should find application in similar high speed camera design problems.