Abstract: Vibrations of a body are measured by attaching a vibrating element to the body, directing a beam of electromagnetic energy onto the vibrating element and collecting reflected electromagnetic energy from the vibrating element. The magnitude of the reflected electromagnetic energy is processed to determine vibration and/or temperature of the body. The magnitude of the reflected light is preferably a function of second degree of the position of said vibrating element. Processing said magnitude of reflected electromagnetic energy is preferably done by a Fourier series up to a second harmonic.

Abstract: This invention relates to a self-aligning bearing for a precision measurement pendulum, in which, between the pendulum and a housing, there are two magnetic bearings, one each on either side of the pendulum, each of which has a bearing ring magnet. The magnetic bearing on the one side of the pendulum has a pole pivot for magnetic centering, opposite which is the pole pivot of a soft iron core. The magnetic bearing located on the other side of the pendulum has a spacer as a mechanical stop, in which there is a tension wire or band stretched between the pendulum and the housing. The magnetic bearings generate magnetic fields of like or unlike polarity extending in the direction of the pendulum axis of rotation, rotationally symmetrically around the latter, and magnetic fields of unlike polarity extending radially to the pendulum axis of rotation, and radially symmetrical to it. The precision measurement pendulum can be used advantageously in a highly-sensitive bearing for measurement purposes.

Abstract: A mismatched path length fiber optic interferometer is optically coupled to an optical fiber and configured to form an omnidirectional acoustic sensor. A second mismatched path length fiber optic interferometer is optically coupled to the optical fiber and configured as a first gradient sensor. A second fiber optic gradient sensor is also optically coupled to the optical fiber. A detector optically coupled to the omnidirectional acoustic sensor and to the gradient sensors converts optical signals output therefrom to electrical signals indicative of the magnitude and direction of changes in an acoustic field. The omnidirectional acoustic sensor may include a length of optical fiber wrapped around the housing while the gradient sensors are mounted inside the housing. The housing perferably has a volume that is adjustable for controlling the buoyancy thereof. Each gradient sensor preferably comprises a pair of mandrels formed to enclose chambers. Optical fiber coils are formed on the mandrels.

Abstract: An accelerometer includes a compliant cylinder supported midway along its length and having equal masses at opposite ends. Two birefringent optical fibers with elliptical cores are wound around the cylinder in opposite senses on opposite sides of the support. Radiation from a source is supplied to one end of both fibers and emerges from the opposite end where it is supplied to respective photodiodes via respective polarizers. Acceleration axially of the cylinder causes extensive strain in one fiber and compressive strain in the other which causes equal and opposite changes in birefringence. A processor subtracts the change in outputs of the photodiodes to provide an acceleration output that is independent of temperature.

Abstract: Force transducers are formed of a beam of polysilicon which is mounted at its ends to a silicon substrate and is encapsulated within a polysilicon shell which defines, with the substrate, a cavity around the resonating beam. The cavity is sealed off from the atmosphere and evacuated to maximize the Q of the resonating beam. The beam is produced by deposition of polysilicon in such a way that, combined with subsequent annealing steps, the beam is in zero or low tensile strain. Resonant excitation of the beam may be accomplished in various ways, including capacitive excitation, and the vibratory motion of the beam may be detected utilizing an implanted resistor which is piezoresistive. Formation of the beam is carried out by depositing the beam on a sacrificial layer and surrounding it in a second sacrificial layer before the encapsulating polysilicon shell is formed. The sacrificial layers are etched out with liquid etchant which passes through channels in the periphery of the shell.

Abstract: The sensor comprises a vibrating sheet (1), mechanically connected to the body (5A) to be analyzed, and an optical triangulation recording system for recording the displacements of the movable part of the sheet, in particular the free end (1B) opposite to that which is restrained. The recording system comprises two optical fibers (7, 9) ending in microlenses (10, 12) having optical axes mutually inclined and converging in the movable part (1B) of the sheet.

Abstract: A method and apparatus for sensing vibrational disturbance using fiber optic coils conducting circularly polarized light. A circularly polarized light source illuminates each of a sensing fiber optic coil in a disturbance-sensitive environment and a reference fiber optic coil in a constant environment, and light from both coils is analyzed through polarization shuttering to detect the degree of polarization rotation thereby to enable determination of frequency and amplitude of the disturbance.

Abstract: Apparatus for determining physical parameters of a disturbance using a fiber optic coil and linearly polarized source light. The apparatus directs a linearly polarized source light through the fiber optic coil being effected by a disturbance, and then measures the effect by comparing optically the source light and the light affected by changes in fiber coil index to detect and develop digital data related to frequency and amplitude of the disturbance.

Abstract: A transducer for measuring vibrations is formed of a case with a vibratory element mounted therein by means of a disk spring which is constrained to vibrate with the vibratory element in a single direction. Optical or magnetic sensors are located in registration with opposed ends of the vibratory element to produce optically or magnetically induced signals having a modulation thereon resulting from vibration of the vibratory element. The use of pairs of the sensors improves signal-to-noise ratio while allowing for increased bandwidth of the transducer in the measurement of vibration.

Abstract: An accelerometer comprises a base and cover together defining a chamber which receives an inertial mass. A diaphragm carries the inertial mass and is bolted between the base and the cover. The inertial mass and the base have facing corrugated surfaces with offset teeth in each of the corrugated surfaces. An optical fiber is clamped between the teeth and extends between the corrugated surfaces. The intensity of light passing through the fiber changes with movement of the inertial mass with respect to the base. The inertial mass moves through the resiliency of the diaphragm, when the base is subjected to accelerations, such as those caused by vibrations. A reference optical fiber may also extend through the chamber above the inertial mass. The same light is supplied to both fibers and the intensity of light from both fibers is subtracted to leave the variation in intensity due to bending of the sensing optical fiber.

Abstract: A fiber optic sensor for the detection of mechanical quantities comprising a light source, a first fiber optic waveguide coupled to the light source, the front face of the first waveguide being ground at a 45.degree. angle to the axis of the fiber and mirrored, a second fiber optic waveguide arranged parallel to the first waveguide, the front face of the second waveguide being ground at a 45.degree. angle to the axis of the fiber and mirrored, the two mirrored faces being held opposite to one another, and a photoelement receiver coupled to the other end of the second waveguide. At least one of the waveguides can move either along the fiber axis or around the fiber axis relative to the other waveguide, the motion varying the light received by the receiver and thereby indicating the magnitude of the mechanical quantity.

Abstract: The movement of a body (1) is determined by mounting on or in the body one or more sources (3,4) and one or more detectors (12,14) such that each source propagates polychromatic light along a path to a detector. Radiation modulation means (19;25) is supported by the body such that a change in the movement of the body causes a displacement of the radiation modulation means in at least one light path to vary the distributed spectral content of the light reaching the detector. The or each detector is adapted to detect the intensity of incident radiation at a plurality of different wavelengths, and analysis means (18) interprets the output of each detector in terms of the movement of the body.

Abstract: A gyro apparatus includes a support in a base table for supporting one end of a vibrating member which has a circular cross-section and which is driven by a drive apparatus mounted on the base table to vibrate it in the longitudinal or axial direction. The vibrating member may be light conducting and a light source sends light through it which is projected onto a light detector so as to detect vibrations perpendicular to the axis direction of the vibrating member.

Abstract: A detector for detecting the acceleration, the velocity or the displacement of a point is described. The detector includes a light source, at least two photoelectric elements spaced apart from each other over a predetermined distance and a focusing optical system disposed between the light source and the photoelectric elements; the combination being particularly suited for use as an optical seismic detector for detecting and mapping an underground stratum structure.

Abstract: A transducer defined by a laser is set forth. Strain, movement, velocity, temperature, pressure, and vibration coupled to the laser change the lasing frequency or form a Doppler shift. The laser is thus installed at a specified location to couple a measured phenomenon and thereby enable transmission of the encoded variable in the laser beam. A receiver located remote from the laser picks up the beam for data retrieval.

Abstract: An optical fiber accelerometer with a rectilinear actuator, such as a push rod, acting on a middle region of an optical fiber pass tautly strung between two supports so that linear actuator motion during sensed acceleration causes lateral displacement of the pass's middle region causing nonlinear (i.e., quadratic) strain in the fiber. This nonlinear response allows the accelerometer to detect acceleration signals in a noisy, low-frequency signal environment through use of a high frequency signal carrier whose amplitude is determined by a low-frequency measured acceleration signal using an optical fiber interferometer.

Abstract: Accelerometer with an inertial mass suspended in a housing, and with apparatus for deriving a signal for the measurement of a force acting on the inertial mass. The accelerometer measurement is thereby made by means of a light source located inside the inertial mass, the light from which is transmitted through hiles in the inertial mass. The light transmitted through the holes strikes photo elements positioned on the housing. This apparatus makes possible a direct evaluation of the signals, whereby, if necessary, digital words can be produced for the determination of the position of the inertial mass within the housing. In one embodiment the inertial mass has two holes therein which transmit light to two groups of photo elements.

Abstract: Vehicular suspension system with apparatus for the measurement of at least one parameter related to suspended and/or nonsuspended vehicle parts. The apparatus has sensing units integrated into a vibration damper. The measurement is thereby made by a light source located inside an inertial mass, the light from which travels through at least one hole in the mass and strikes one or more photo elements located in the inside wall of a housing. This apparatus makes possible a direct evaluation of the signals. If necessary, digital words can be formed by different photo elements and holes for the determination of the position.

Abstract: An optical-electrical geophone which generates a binary signal is described. The geophone utilizes an optical fiber for the return transmission of a light source in the geophone. The geophone contains a light chopping means which oscillates in response to vibrations imparted into a geologic formation. As the chopping means such as a baffle or a tubular member vibrates, it chops the light signal and creates an on/off light pattern, i.e., binary signal. The light passing through a slit in the baffle or tubular member is returned to the seismic vehicle through an optical fiber for further processing. The optical-electrical geophone creates a binary signal directly without the use of clipping electronics and magnets or coils used in conventional geophones.

Abstract: An accelerometer is disclosed, which includes a flexible hinge, a base table fixed with one end of the flexible hinge, a pendulum fixed to the other end of said flexible hinge, torquers for producing a torque proportional to acceleration applied from the base table to the pendulum and a displacement detecting apparatus for electrically detecting a relative displacement between the fixed portion of the base table and the pendulum, wherein the base table is formed of first and second frames, the first frame is provided with an engagement portion for engaging with the second frame, a fixed portion for the flexible hinge, a fixed portion for the displacement detecting apparatus. In this case, the first frame is provided at its outer peripheral portion with an attaching flange portion and, one plane of the flange portion is used as an attaching reference plane for attaching the accelerometer to a body the acceleration of which is to be measured.

Abstract: The inside surface of a conductive vessel (preferably spherical) with insulated adjacent segments is coated with a dielectric layer. The vessel is then partly filled with a conductive liquid-like material such as mercury having an upper surface which remains approximately horizontal irrespective of the inclination of the vessel. The capacitance between the segments and liquid varies as a function of the vessel's inclination. Vibration-induced surface action also produces varying capacitance which can be detected for seismometer applications and the like.

Abstract: A wide bandwidth, high sensitivity optical accelerometer having a lever arm to amplify the mechanical displacement of the accelerometer mass element. The optical accelerometer includes a high resonant-frequency spring-mass system, wherein the acceleration forces up to several hundred Hz cause a linear displacement of the mass with force, which, through the lever arm, modulates the intensity of a beam of light with a large gain. The modulated light beam is in turn converted to an electrical signal which corresponds to the applied accelerating force. The accelerometer of the present invention may be largely fabricated from a single piece of material such as silicon, wherein the lever, mass, spring and supporting structure are etched from a single substrate according to known photolithographic processes. Alternatively, the accelerometer components may be molded from a sheet plastic or other material.

Abstract: A hydrophone streamer that includes several arrays of optical fiber pressure sensors. Each array consists of at least three sensors symmetrically disposed around the inside of the streamer skin to form a vertically-disposed array. Each sensor modulates a coherent light beam in accordance with the instantaneous ambient water pressure. The output signals of the sensors include an AC component due to seismic waves and a DC component due to hydrostatic pressure difference between the sensors of an array. Means are provided to resolve the AC and DC components to determine the arrival direction of the received seismic waves.

Abstract: A vibration sensor is constructed by providing two preferably matched coils of fiber-optic material. When the sensor experiences vibration, a differential pressure is exerted on the two fiber coils. The differential pressure results in a variation in the relative optical path lengths between the two fibers so that light beams transmitted through the two fibers are differently delayed, the phase difference therebetween being a detectable indication of the vibration applied to the sensor.

Abstract: A transducer device for translating increments of linear displacement by means of opto-electronic sensing into increments of units expressed into units of volts. The device comprises an opto-electronic system, having a pair of co-planar, adjacently disposed radiation sensitive surfaces of square configuration, and a thereto facing, closely spaced surface of rectangular configuration being designed to emit a uniform pattern of radiation over its entire active surface. Wherein, the geometry of the emissive and sensing surfaces during relative movement provide a ratio of produced volt equivalent to the ratio of relative displacement between the emissive and sensing surfaces.

Abstract: A spring-suspended mass has top and bottom reflectors. A laser light beam is divided into separate beams that are reflected from the top and bottom reflectors into photo detectors. At the photo detectors, a reference beam from the same laser is recombined with the two reflected beams to produce two interference fringe patterns in response to seismic disturbances of the mass. A count of the number of fringes and fractions thereof that are detected over a unit time interval is proportional to velocity of the mass in terms of the wavelength of the laser beam. The phase difference between the two interference fringe patterns is a measure of polarity of the seismic disturbances.

Abstract: Photoelastic sensing means, and more particularly photoelastic sensing means capable of providing high sensitivity for measuring pressure, force, displacement, acceleration or inertial force, proximity, temperature and other measurands. The photoelastic sensing means comprises a thin photoelastic member of transparent material having closely spaced top and bottom outer surfaces with peripheral edges and an edge surface extending between the peripheral edges of the other surfaces. Light flux is provided to the edge surface of the member at a first region for transmission by the member along a path to a second region at the edge surface where it is received and detected. The spacing between the top and bottom outer surfaces of the member is relatively small compared to the length of the path of the light flux in the member. The member is supported to produce bending stresses in the member in a direction transverse to the path of the light flux in the member with the application of force to the member.

Abstract: An accelerometer utilizes a laser source, a photoelastic waveguide, a plurality of optical beam paths and detectors for processing optical output energy from the laser along two or more paths for providing phase detection for measuring acceleration. An electronic signal processing section converts the optical signals to electrical signals and provides an output for indicating circuitry. Formed in a micro-optical/integrated optic format, the accelerometer can be packaged in a small volume which allows ready use in systems for guidance or navigation purposes. Light generated by the laser is divided into two or four beam paths. Beam energy is directed through the photo-elastic waveguides and are selectively recombined to set up interference conditions. Subjecting the waveguide to acceleration stress will cause a detectable phase difference to occur which is indicative of acceleration.

Abstract: An apparatus for determining levels of physical loads, having a housing with two switching elements disposed therein and electrically coupled to an indicator and through a cut-out switch to a power supply unit. The apparatus further comprises a seismic mass constituted by a permanent magnet and secured in the housing by means of elastic suspension elements. The switching elements are positioned along the direction of movement of the seismic mass. The indicator includes three indicating elements indicating, respectively, the minimum, the optimum and the maximum level of physical load.

Abstract: A light beam is transmitted by a fiber optical cable to a light modulation device such as a vibrating filament, bar or plate. This device or oscillator modulates the light intensity with a frequency which is dependent upon the physical parameter to be measured. Oscillations are sustained by a striking device. The modulated light beam is transmitted by a fiber optical cable from the measurement location to an evaluation location where the frequency of the modulated light beam is measured. The measured frequency is a function of the physical parameter.

Abstract: A fiber optic angular accelerometer is provided by employing a flexible membrane having an optical fiber attached thereto, an input optical fiber for coupling light to the fiber attached to the flexible membrane and an output optical fiber for receiving light from the optical fiber attached to the flexible membrane whereby angular accelerations will occasion flexing of the flexible membrane and cause the optical fiber attached thereto to pivot about the point of attachment and occasion a change in light transmitted between the input and output optical fibers.

Abstract: The deflection, due to inertia, of the free end of the cantilever rod of fiber optic material is an indication of the acceleration of the supporting structure of the rod. The indication of the deflection of the rod is by detecting light propagating the free end of the rod. Disclosed are fiber optic rod sensing element structures for acceleration indicators, a rate of change of acceleration indicator, a rotation indicator, and a latching acceleration indicator.

Abstract: The invention relates to a fiber optical device for measuring physical magnitudes such as force, elongation, pressure, acceleration, temperature, etc., comprising a transducer unit and an electronic unit, in which the quantity to be measured is supplied to the transducer unit to affect the resonance frequency of an oscillating body included in the tansducer unit by changing the dimensions, mass, density, modulus of elasticity and/or mechanical stress of the body. A property of the body oscillation, such as frequency, phase position and/or amplitude, is used as a value of the quantity to be measured. The oscillations of the body are detected optically by means of a fiber optical position/movement detector.

Abstract: The amplitude of mechanical vibration of a surface is measured by a photonic sensor coupled to an electronics package. The sensor is mounted inside a sensor housing which is inserted into a bore within a base housing. The base housing may be attached to a seismically independent surface or to the vibrating surface itself. The sensor housing is biased toward the open end of the bore in the base housing so that it contacts the vibrating surface, placing the sensor in communication with the vibrating surface. In this configuration, the sensor housing will remain substantially stationary at one peak of the vibration, tracking thermally induced changes in the position of the vibrating surface while the sensor and attached electronics package measures the amplitude of the surface vibration.

Abstract: A mass is attached between light reflective ends of a pair of rectilinearly aligned optic fibers and maintained in such position with the fibers under a slight tension. The pair of fibers comprise a portion of two arms of a Mach Zehnder or Michelson interferometer so that an acceleration along the longitudinal axis of the rectilinearly aligned optic fibers increases the length of one of the pair of fibers and shortens the length of the other, whereby electromagnetic rays traveling in the pair of fibers, travel different distances resulting in a phase shift which phase shift is directly proportional to the force applied to the fibers by the mass and therefore directly proportional to the acceleration. Accelerations in directions perpendicular to the longitudinal axes of the fibers cause equal phase shifts in each arm and therefore would not be detected. Thermal expansion of the fibers and acoustical noises should also balance out.

Abstract: A vibration detector having a mass pivotally mounted in a housing, means for sensing the vibration of the mass and means for damping the vibration of the mass has been found. The sensing of the vibration of the mass is performed through a combination of an optical and electrical means. The mass has a mirror, and an optical path from a fixed light source to a fixed light receiving plane through the mirror on the mass is provided. A beam sensor mounted at the light receiving plane, said beam sensor having a plurality of cells, senses the presence of the light beam from the light source through the mirror on each cell. The parallel light beam illuminates the specific cell depending upon the vibration of the mass and the illuminated cell provides an electric output signal indicating the reception of the beam. Thus, the vibration is detected as the electrical output of each cell.

Abstract: An omnidirectional hydrophone using particles suspended in a liquid acoustically coupled to a conducting environment for detecting acoustic waves by providing scattering of internally generated electromagnetic radiation from particles driven by the acoustic waves.

Abstract: A vibration detector having a pendulum, means for sensing the vibration of the pendulum, and a means for damping the vibration of said pendulum has been found. The pendulum has a light source which provides a parallel light beam, and the parallel light beam focuses at a light receiving plane. A beam sensor mounted at the light receiving plane, said beam sensor having a plurality of cells, senses the presence of the light beam on each cell. The parallel light beam illuminates the specific cell depending upon the vibration of the pendulum, and the illuminated cell provides an electric output signal indicating the reception of the beam. Thus, the vibration is detected as the electrical output of each cell. The relationship of the light beam and the light receiving plane can be inversed, that is to say, the light beam can be fixed and the light receiving plane can be mounted on the pendulum.

Abstract: An optical seismograph which functions to measure the relative movement of a beam of electromagnetic waves connected to the extremities of a plurality of pendulums and includes a collimated source which delivers a parallel beam of electromagnetic waves and a plurality of pendulums whose oscillation paths are perpendicular to one another, means fixed in relation to the electromagnetic wave beam direct the luminous beam on the heavy extremities of the various pendulums; and photoelectric means to measure the position variations of the extremities of the pendulums in relation to the electromagnetic wave beam. The seismograph is suitable for the detection of earthquakes.

Abstract: A fluid film levitated horizontally oriented disc is self-centering and floating above another similar mating surface stationary disc. A means for varying the natural period of free oscillation of the levitated disc within the normal earthquake band of frequencies and a means for damping out such free oscillations along with a means for transducing positional differences between the discs into signals wherein earth tremors arriving from any horizontal direction may be recorded.