The effect of end spacing between fiber optic image conduits is considered. The spatial resolution and photometric transmission are considered with and without the use of immersion fluids. The gains in both resolution and transmission when using an immersion fluid are demonstrated with experimental data. Some practical applications, where immersion fluids can be used, are discussed.

An automatic tracking system which encompasses the capability of recording the target offset from the optic axis of the tracking instrument directly in binary form on magnetic tape is presently being developed at NOTS. This system is designed to operate on the video signal and raster pulses from any closed-circuit TV, either vidicon or image orthicon. Counting lines from the top of the frame to that on which the desired video signal occurs gives the vertical position of the target in the frame, while a second high-speed counter records pulses from a self-contained clock-oscillator during the interval between the target pulse and the end of the TV line on which it occurs. Digital-to-analog conversion utilizes the stored counts to provide control voltages for an amplidyne-driven mount. Operating characteristics are discussed; test results are presented and analyzed.

An image converter tube contains a photoemissive surface which emits electrons from each small area in proportion to the intensity of light striking it. The electrons are pulled away from the surface, or photocathode, by an electric field and accelerate through a vacuum to a fluorescent screen. An electron lens may be used to bring together all of the electrons emitted from any point on the photocathode to a corresponding point on the screen, creating an electron image of the light intensity pattern on the photocathode. The phosphor converts the electron energy to light, recreating the original optical image.

A high speed photo recording system is now being used in a basic study of crack propagation velocities during brittle fractures occurring in transparent materials. Velocity measurements of 7.1 x 104 cm/sec. have been recorded with time resolution of less than 1 microsecond. The camera, lighting system, trigger circuit, impact equipment, and planned future studies of brittle fracture phenomena will be discussed.