Abstract: A laser interferometer or a single aperture Laser Doppler Displacement Meter (LDDM) is used to measure the precise position of a ninety degree notch or a flat reflecting surface on a rotating arm. For the case of using the ninety degree notch, a stationary flat mirror is used to reflect back the laser beam which follows the same beam path but in the opposite direction to the receiving aperture. For the case of using a flat reflecting surface, a stationary corner cube and a stationary flat mirror are used to reflect back the laser beam which follows the same beam path but in the opposite direction all the way to the receiving aperture. For both cases, the laser beams remain aligned even though the arm rotates a large angle. Hence, the position of the rotating arm can be determined. Since the notch or flat reflecting surface is attached or integral part of the arm, the disk drive can be enclosed with the laser beam passing through a window. Hence, the technique described is non-intrusive.

Abstract: Apparati and methods are disclosed for detecting vibrations, displacements and motions of a remote surface with high sensitivity, high frequency response and high accuracy using a laser beam with optical modulation, optical hetrodyning and phase detection. High speed digital signal processing is used. Shared aperture design is employed for utilization of a flat target, double-pass design for large lateral movement tolerance with high resolution, and dual target design for detection of displacement as well as angular changes in vibrational motion.

Abstract: Apparatus for the precise measurement of the displacement of a moving cooperative target from a reference position, traveling, for example, over a distance of several meters, and with the measurement accuracy being better than a fraction of a millimeter. The apparatus includes a low-cost laser which generates a beam of a selected frequency. The laser beam is directed at the moving target and is reflected by the target. The apparatus also includes additional elements which measure the Doppler phase shift of the reflected laser beam so as to obtain a precise measurement of the displacement of the target with respect to the reference position.

Abstract: Laser emission from rare gas-halogen molecules, particularly krypton fluoride, is produced by a chemical reaction initiated by an efficient, high-power, high repetition-rate, fast electric discharge device transferring energy directly to a body of the gas in a laser cavity. The discharge device is of Blumlein parallel plate condensor/conductor type in which the condensor plates and their separating dielectric are uniformly compressed within an evacuated chamber by the force of the external atmospheric pressure.