Abstract: The laser brazing of the present invention offers the unique advantage of producing a high temperature hermetic bond while limiting the heat affected zone to the region of the joint. Laser brazing joins infrared (IR) and radio frequency (RF) ceramic materials to metals for radome applications. Using AG--Cu--Ti brazing alloys, zinc sulfide (ZnS) infrared windows were laser brazed to cylindrical titanium housings with no thermal degradation observed in crystalline properties of ZnS. Innovative glass-ceramic materials were also used as braze filler to produce over 30 ceramic-to-metal couples, including titanium Zns, Pyroceram/Kovar and niobium/sapphire. Benefits are in the production of strong, high temperature, hermetically sealed joints in aircraft and high velocity missile systems. An optimized laser brazing system is provided.

Abstract: An improved method and apparatus for optically sensing and measuring physical quantities such as magnetic fields, electrical fields, mechanical strain, temperature, sound and pressure. The apparatus aspects of the invention involve a sensor structure consisting of a sandwich of magnetostrictive, piezoelectric or other materials sensitive to the physical quantity measured which are spaced apart by two opposed parallel reflecting surfaces located on opposing sides of the sensitive material. The reflecting surfaces can include an array of plane mirrors, diffraction gratings, curved mirrors, or retro-reflecting spheres. In its method aspects, multiple optical reflections between the two surfaces provide a magnified optical phase shift when the shape of the slab that is sensitive to changes in the applied field causes mechanical strains in the material. The changed optical signal can be measured by a suitable measurement device such as an interferometer for phase comparison with a diffraction reference pattern.

Abstract: An all digital eddy current measurement system is described and illustrated in which an eddy current probe is driven by a driving signal and voltage signals representing the current through and voltage across the probe coil are used to calculate the magnitude and phase angle of a complex probe impedance. Digitization of the voltage signals is controlled by a control logic system which is run separately from but initiated by a microprocessor, the latter of which functions to analyze the acquired data and calculate impedance magnitude and phase angle values therefrom.