An Electro-Optical Shutter for Photographic Purposes

Abstract

This paper presents the theory and describes the development of a simple, reliable, and compact optical shutter which utilizes a Kerr cell as a light valve. With the aid of such a shutter, routine photographic studies of electric discharges have been made using an effective exposure time of 0.000,000,04 second. The novel feature of an electro-optical or Kerr cell shutter is that there are no mechanical moving parts, the speed of operation depending only upon the rapidity with which a required voltage can be applied to the Kerr cell electrodes. These electrodes are immersed in a fluid which exhibits uniaxial birefringence when under the influence of an electric field. Electrical birefringence is described and explained at some length and the optical transmission of a Kerr cell shutter as a function of applied voltage is derived and plotted for reference. With the advent of the ``all-electric'' shutter, some of the latest techniques of the electronic art become applicable to photographic work. The control can be made sufficiently positive and accurate to permit initiation of operation at any preselected instant with a precision of 5×10 ^-9 second. This excellence of control has made possible the detailed photographic study of light from very rapidly changing self-luminous objects. The complete components of an electro-optical camera are described in some detail. Prints are included which show photographic records of the electrical vaporization of a fine wire taken with an effective exposure time of 0.000,000,04 second.