Abstract: A method and apparatus for aligning the light path of a square ring laser gyroscope wherein the alignment method includes directing two input beams of light into the cavity of the gyroscope. Next, the input beams are intercepted prior to their incidence upon the input mirror with a pair of polarizers. Subsequently, the extinction ratios of the first and second output beams of light are measured at the exit mirror. The curved mirrors of the gyroscope are then translated in opposite directions and equal amplitude so as to change the extinction ratios of the output beams. Such translations are repeated until the measured extinction ratios are substantially equal.

Abstract: A test system for optical disks, comprising a spindle motor for clamping and rotating an optical disk at a constant speed; an encoder for generating a pulse output corresponding to the angle of rotation of the motor; a measuring head comprising focus and tracking servo mechanisms for causing the focal point of a laser beam irradiating the disk to follow the guide groove thereof, and a displacement detector for optically detecting the displacement of a focusing lens driven by the servo mechanisms; the measuring head being operative to generate an output signal proportional to the displacement of the focusing lens; a feed mechanism for moving the measuring head in the radial direction of the disk; a control circuit for controlling the operations of the motor, the servo mechanisms and the feed mechanism; an analog to digital converter for converting the output of the measuring head at a timing according to the pulse output of the encoder; and a computer for commanding the control circuit and for computing the ou

Abstract: Disclosed is a ring laser angular rate sensor constructed from a solid block with mirror assemblies joined to the block with a thermally formed gas tight seal. The mirror assemblies include a coating of alternating layers of zirconium dioxide (ZrO.sub.2) and silicon dioxide (SiO.sub.2) which have been ion beam sputtered on mirror substrates composed of a material which suitably matches the thermal coefficient of the laser block.

Abstract: The optical fiber interferometer system is used either in a gyroscope or else for measuring electrical current by the Faraday effect. It includes an optical board (100) which is connected to the two ends of a monomode optical fiber (200) constituting an interferometer ring, said optical board including a photodetector (103) which is colinear with the light source which is coupled by both its front and its rear faces. The two counter-propagating beams travelling round the interferometer ring have their relative phase difference modulated by phase modulation and their light power modulated by amplitude modulation. An electronics board (300) generates these modulations and, from the photodetector signal (103), it extracts a component at the lower beat frequency between said two modulation frequencies, thereby making it possible to measure the relative phase difference between the two beams.

Abstract: An apparatus for remotely orienting the distant tip of a flexible borescope cable to point in a desired direction utilizes a plurality of vertabrae-like annular disks disposed transversely within the hollow interior of the distal end of the flexible cable. Fine, flexible wires fabricated from a shape memory effect (SME) alloy are fixedly attached to outermost disk, and extend longitudinally backwards slidably through aligned holes in the other disks, and slidably through hollow flexible tubes rearward of the innermost of the disks.

Abstract: A ring laser is provided with at least one retroreflector external to the ring laser closed-loop path for redirecting energy extracted from one of the counterpropagating beams into the opposite traveling counterpropagating beam. The redirected energy is modulated so as to oppose the normal coupling between the counterpropagating beams which causes lock-in.

Abstract: A correction to the output angle of the ring laser gyroscope is calculated as a function of the phase difference and the magnitude of coupling between the two counterpropagating beams when the dither oscillations change direction. A pair of heterodyne detectors produce heterodyne signals indicative of the interference pattern between the counterpropagating beams. A signal indicative of the sum of the separate beam intensities is demodulated with the heterodyne signals to determine the magnitude of coupling between the beams in the ring laser gyroscope.

Abstract: An interchangeable beam splitter holder includes a retainer which holds the beam splitter, and a front door and rear door which are both hingedly connected to the retainer. The doors are movable between a closed position, in which the doors substantially cover the beam splitter, and an open position, in which the doors are pivoted upwardly so that the beam splitter is exposed. The beam splitter holder also has three adjusting screws with ends which are adapted to abut against pivot points in the interferometer to thereby align the beam splitter. The beam splitter holder also has three spring plungers which abut against surfaces within the interferometer to push the ends of the adjusting screws against the three pivot points in the interferometer.

Abstract: In a method of evaluating the thermal stability of hydrocarbon liquid fuels, the fuel flows over a heated tube that causes the fuel to decompose and deposit a residue as a film on the surface of the heated tube. The thickness of that residue film is a measure of the fuel's thermal stability. To measure the film's thickness, the film is illuminated with light that is substantially monochromatic. The light reflected from the surface of the heater tube interferes with the light reflected from the overlying surface of the residue film on that tube and thereby causes variations in the intensity of the reflected light. Those variations in intensity of the reflected light are detected to obtain a measure of the thickness of the film. In one embodiment of the invention, the heated tube is situated in an enclosed housing through which the fuel is caused to flow and the thickness measurement is made while the film builds up on the heated tube.

Abstract: A Sagnac interferometer gyroscope including periodic generator driving an optical modulator coupled to one end of the fiber optic loop, the signals from the fiber optic loop being coupled through two feedback loops. The first feedback loop operating on a signal equal to the twice the periodic generator signal frequency which is integrated and supplied, together with the signal from the periodic generator to a summing circuit to drive the optical modulator such that it maintains the measurement of the gyroscope output through specific quad points. The second feedback loop operates on a signal at a frequency equal to the frequency of the periodic generator and provides the integrated value of this signal after demodulation to summing circuit, together with a calibration signal, the output signal from the summing circuit being applied to a line stretcher element in the Sagnac fiber optic loop to maintain the output signal at a constant scale factor.

Abstract: A structural element is provided with at least one light conduit which is arranged thereon under a selected mechanical initial stress. In this manner, the deformation or breakage can be detected at loads or deformations which are lower than the breaking loads or deformations of the component parts to be monitored.

Abstract: A double-path interferometer comprises first and second polarized beam splitters disposed side by side on a light path from a light source, a half-wave plate interposed between the first and second polarized beam splitters, a cube corner prism, a reflecting mechanism disposed on the light path of the cube corner prism ahead of the two splitters, and a quarter-wave plate for causing a 90-degree rotation of the polarization plane in forward and backward light paths with respect to the reflecting mechanism.

Abstract: A system and method for detecting the influence of selected forces on an interferometer over an extended dynamic range. One presently preferred embodiment is disclosed for detecting rotation of an interferometer. In this embodiment, an open-loop, all-fiber-optic gyroscope provides an output signal comprising the phase difference of two light waves which are counterpropagating within the gyroscope, and which are phase modulated at a selected frequency. The phase difference of the light waves is influenced by the rotation rate of the interferometer. The output signal is amplitude modulated at the phase modulation frequency to transpose the optical phase shift into a low frequency electronic phase shift, which is measured using a digital time interval counter. A linear scale factor is achieved through use of this system and method.

Abstract: A test system for optical disks, comprising a spindle motor for bearing and rotating an optical disk at a constant speed; a measuring head, comprising focus servor and tracking servo mechanisms for causing the focal point of a laser beam irradiating the optical disk to follow the guide groove of the disk, for generating an output signal proportional to the intensity of the reflected beam coming from the optical disk; a feed mechanism for moving the measuring head in a radial direction of the optical disk; a control circuit for controlling the operations of the spindle motor, the focus servo and tracking servo mechanism of the measuring head, and the feed mechanism; a measurer for performing desired measurements in response to the output signal from the measuring head; and a computer for commanding the control circuit and the measurer and for processing the measured data of the measurer, whereby all the measurements are accomplished with the guide groove of the disk being under the focus and tracking servos.

Abstract: The interferometer makes use of an acousto-optic device to perform a frequency shift of the beam sent along one of the interferometer branches, so as to allow the determination of the state of polarization by heterodyne radiofrequency detection. The acousto-optic device can be inserted downstream of the device for splitting the beam emitted by the source into the two beams sent along the two interferometer branches, or it can also act as the beam splitter.

Abstract: An image enhancer for providing a sharp, contrasting image of a pattern, such as a fingerprint pattern is disclosed. In one embodiment, an image enhancer is comprised of a viscous, opaque liquid interposed between an optical glass window and a reflective elastomeric membrane. Artificial lighting is evenly focused on the underside of the membrane and a sharp fingerprint image of a finger pressing said membrane against the window is produced. The image can be either photographed or focused on a conventional matrix of image sensors or pixels.

Abstract: An interferometer bearing assembly including a fixed glass rail, a movable carriage that carries both the movable interferometer mirror and the drive coil for the linear motor, and a mechanism for biasing the carriage onto the rail. The glass rail has two optically flat faces defining a normally horizontal line of intersection. The carriage is a rigid structure with plastic surface portions that provide a bearing interface for contacting the flat faces of the glass rail. To improve stability and reduce the possibility of any transverse movement, the carriage is downward biased, preferably by providing an overlying glass plate with a downwardly-facing flat surface, and mounting a spring-loaded plastic element to the top of the carriage. The plastic element contacts (and slides along) the flat glass surface and transmits a downward force to the carriage.

Abstract: Readout signals of a dithered ring laser angular sensor are processed by a signal combining circuit which forms part of a closed-loop dither signal remover scheme. The output of the signal combining circuit is demodulated as a function of the dither applied to the ring laser sensor and subsequently utilized to control a correction signal. The signal combining circuit combines the readout signal and the correction signal to yield an output signal stripped of substantially any dither signal components.

Abstract: An apparatus and method for path length control for a laser gyro using two external gain cells and the shifted gain spectra of two neon isotopes. The laser cavity is stabilized by detecting the difference in the amplification rate between the two gain cells that are traversed by two rays. Absorption cells may be used to replace the gain cells.

Abstract: A light-activated PIN diode switch arrangement is coupled to a source of direct voltage and to a load for control of the flow of load current. The PIN diode switch arrangement is connected so as to be electrically reverse-biased, so that no current flows therethrough. A source of light is coupled to the active portion of the PIN diode switch arrangement for rendering it conductive when flooded with light. Higher reverse voltage capability, higher operating speed and lower overall forward resistance are simultaneously achieved by a plurality of series-connected PIN diodes by comparison with a single large PIN diode.