Abstract: A detector is described, intended for use in metrology systems of the type which produce interference fringe patterns which contain a phase which is characteristic of the parameter under measurement, particularly displacement or position. The detector is in the form of an array of elements whose outputs are electrically interconnected so as to form three or more signals displaced from one another in phase by a fixed amount. The detector is provided on a single monolithic, silicon substrate using microelectronics techniques.

Abstract: A metrology system includes means for generating an interference fringe pattern as a function of a parameter to be measured, transducer apparatus for simultaneously generating three intensity-modulated optical signals, I.sub.R, I.sub.S and I.sub.T, that are related to the interference fringe pattern; signal processing apparatus for accurately determining an aspect of the interference fringe pattern from the three signals; means for accumulating phase information proportional to the aspect of the interference fringe pattern; and means for converting the accumulated phase and aspect information to desired outputs indicative of the parameter to be measured.

Abstract: Frequency stabilization is disclosed for a laser device, wherein the laser tube is provided with end mirrors which are mounted in extensions at the respective ends of the laser tube. The laser tube extensions have reduced sections which are movable to allow adjustment of the end mirrors in the laser device. The reduced sections are preferably made of metallic material. The means to stabilize frequency provided is the application of heat or current or both to and around a reduced metallic section in the laser tube extension. This may be accomplished by the passing of current through a wire wrapped around the reduced metallic section. The passing of such current causes the reduced metallic section to contract and expand along an axis in line with the laser tube, and as well as a magnetic field is induced upon the gaseous medium within the laser tube. By such means controlled by suitable circuitry, laser frequency stabilization is accomplished.