The use of methods of experimental mechanics to study physical behavior in elasto-dynamic problems requires high speed photographic recording systems capable of storing images of optical fringe patterns where features often propagate at or above the dilatational wave velocity. This paper discusses the requirements of a very high speed recording system for the dynamic photomechanics class of experiments. The requirements include: exposure time, framing rate, field size, image size and light intensity. The design of a new Cranz-Schardin photographic recording system which has recently been completed at the University of Maryland is described in some detail. The camera system incorporates a novel spark gap design with a reflecting and focusing mirror and a fiber optic output. The fiber-optic bundle adds considerable flexibility in adapting the optical system to a large number of different experiments. The optical system has been designed for operation in both the transmission and reflection modes. In the transmission mode the system records conventional photoelastic fringe patterns, moire and caustic images of transparent media. In reflected light the specimen is mirrored and the system records fringe patterns from birefringent coatings, moire and caustic images from opaque materials.
James W. Dally,
Robert J. Sanford,
"Applications Of Photoelasticity To Elasto-Dynamics", Proc. SPIE 0814, Photomechanics and Speckle Metrology, (17 February 1987); doi: 10.1117/12.941656; https://doi.org/10.1117/12.941656