Abstract: An optical fiber transducer system employs a single optical fiber that carries an optical carrier signal to a remote transducer location and also carries a multiplexed multichannel signal, each channel having a characteristic delay and a binary amplitude value, to a receiving unit, where each channel of a set of reference signals having a corresponding characteristic delay interferes with the multiplexed signal to separate a channel signal that is envelope detected.

Abstract: The present invention concerns a unique vibration detector for sensing movement or vibration of an associated object. The detector includes an infrared light transmitter positioned to direct light toward a reflective fluid mass such as, for example, mercury. A cooperating infrared receiver is positioned to receive at least a portion of the light reflected off the fluid mass. As the object and detector are vibrated, the surface of the fluid will be disturbed, thus varying the amount of light energy detected by the receiver. In the preferred embodiment of the invention, the fluid mass of mercury is contained within a cylindrical chamber having a relatively small diameter such that the upper surface of mercury provides a generally convex-shaped reflecting surface. The vibration detector can be utilized, for example, in a vehicle anti-theft system.

Abstract: The disclosure is directed to an improved a seismic detector comprising: a container for containing liquid therein, liquid means being contained in the bottom of the container, a source of light for illuminating the inside of the container, a sensor means having at least one photoelectric device for transforming the light inside the container into electric signals, and a signal processor means for generating an output when the output of the sensor means exceeds a predetermined value.

Abstract: Sound intensity is determined by simultaneously measuring instantaneous acoustic pressure and instantaneous particle velocity at a single point. A condenser microphone having a vibrating diaphragm generates an output voltage proportional to the instantaneous acoustic pressure. A laser Doppler vibrometer measures the velocity of the vibrating diaphragm and a Doppler frequency tracker converts the velocity measurement into another output voltage which is proportional to the instantaneous acoustic particle velocity. The sound intensity is then calculated from the known components.

Abstract: An object to be inspected which is jointed to a circuit board is vibrated in a contactless manner by applying a gas jet or a magnetic force to the object, a laser beam is irradiated on the object, and a laser beam reflected from the object is detected by a linear sensor to observe a laser speckle pattern for the object. Quality of a joint junction state of the object is judged from the laser speckle pattern.

Abstract: The invention is concerned with a laser heterodyne interferometric method and system for measuring the displacement of a free surface of a material subjected to ultrasound. A laser beam having a predetermined intensity is generated and then divided into first and second beam portions having respective intensities representing minor and major fractions of the predetermined intensity, the first beam portion being angularly displaced relative to the second beam portion and being frequency shifted by a predetermined frequency. The second beam portion is passed through an optical lens off-center thereof to focalize the second beam portion onto the free surface of the material subjected to ultrasound, thereby scattering same. The scattered second beam portion is combined with the first beam portion to obtain an optical fringe signal which is converted into an electrical fringe signal comprising a central peak at the predetermined frequency and a sideband on either side of the central peak.

Abstract: An improved bifurcated multi-lever fiber optic transducer comprising one ht transmitting fiber and two receive fibers having different core diameters separated at one end and combined at the common distal end in the vicinity of a reflective surface parallel to the fiber end plane which is sensitive to axial motion caused by minute pressure changes, either in air or water, such that any displacement of the reflector from equilibrium will increase or decrease the illuminated areas of the two receive fibers which can be used to generate a processed output signal proportional to this motion. The resulting probe is of minimal diameter, has significantly improved sensitivity and produces an output independent of power variations at the input.

Abstract: An optical telemetric system for use in a borehole consists of a bidirectional optical fiber to which are coupled a plurality of acousto-optical seismic sensors. The sensors consist of an optical cavity that becomes resonant at certain wavelengths depending upon parameters of cavity length and index of refraction. Those parameters are capable of being modified on the basis of static and dynamic pressure differences within the borehole. A swept-wavelength laser chirp pulse is launched into the bidirectional optical fiber. The static pressure at each sensor establishes a resonant wavelength that serves as a carrier signal. Dynamic pressure changes due to seismic waves, modulate the carrier signal. The modulated carrier signals from each sensor are reradiated through the bidirectional optical fiber in a wavelength-division multiplexed format. The multiplexed signals are received by and demultiplexed by a suitable signal receiving apparatus.

Abstract: The surface of a specimen to be inspected is irradiated with a light having an intensity which varies from a position distant from the material, so that ultrasonic beams are generated in the material to be inspected. A coherent light is also projected onto a fixed surface provided at a given position and onto the surface of said material to be inspected. Vibration generated in the surface of said material due to ultrasonic beams reflected by a defect in the material, is detected in the form of change in phase of the coherent light that is reflected by the surface of the material. The change of difference in phase between the coherent light reflected by said fixed surface and the coherent light reflected by the surface of the material is measured with the lapse of time, in order to detect the flaw.

Abstract: A fiber optical measuring device for measuring dynamic movements between a boundary surface of an optical fiber and a boundary surface of a movement-sensing body. The optical fiber is adapted to transmit optical energy to and from the boundary surfaces and at least one of the boundary surfaces includes a photo-luminescent material, the optical energy reflected from the boundary surface of the body being dependent on the relative position between the two boundary surfaces.

Abstract: An optical vibration analyzer is disclosed in which a fiber optic probe collects back scattered light from a vibrating surface illuminated with non-coherent light. The probe is positioned very close to the vibrating surface such that the amount of light scattered back into the fiber optic probe varies with the instantaneous relative separation between the probe and vibrating surface. A photo-diode detects the varying average intensity of light received by the probe and generates a light intensity signal which is amplified to a usable level. The back scattered light is very small in comparison with ambient light and other non-correlated noise from which it is extracted. Accordingly, vibrations in the observed surface are excited by a sweep oscillator and the received signal is processed through a tracking filter locked to the sweep oscillator. The filtered output is monitored and varies directly with the vibration amplitude of the surface.

Abstract: A system for the examination of a test object for internal flaws (or acoustic discontinuities such as solid-to-gas or solid-to-liquid interfaces) by means of ultrasonic waves. The ultrasonic waves 18 are induced in the object 16 by projecting at least one intense, pulsed laser beam 13 on the object 16 and scanning the beam 18 along the object 16. Another laser beam 23 is projected on the object 16, either opposite the first beam 14 or on the same side adjacent to the first beam 14, so that is reacts with and is frequency-modulated by the ultrasonic wave. The reflected, frequency-modulated beam 24 is fed to an optical heterodyning means 26 which passes through only an optical beam 28 modulated with the ultrasonic frequency to a photodetector 30.

Abstract: An electret sheet is clamped on an apertured support around the aperture so that a sheet portion stretches all across the aperture. A tension-producing ring is advanced against the sheet portion normal to its stretch direction to produce progressively increasing tension therein. Concurrently, a loudspeaker on one side of the sheet emits constant-amplitude sound waves of fixed frequency and directed against the sheet portion to cause it to vibrate at that frequency. When, because of the increasing tension in the sheet portion, it's vibration amplitude rises to a predetermined value at or near resonance, the advance of the mentioned ring is ended, and the sheet portion is adhered to another ring which retains in that portion the tension then existing in it. Such tensioned sheet and adhering ring are then used to make electret diaphragms for electret microphones.

Abstract: A fiber optic device senses the generation of vortices by measuring the torsional displacement of a bluff body mounted for rotation about its center of inertia within a fluid conduit. An internally toothed member is fixed to the outside of the fluid conduit, and an externally toothed member is fixed to the bluff body for rotation therewith and is in partial meshing relation to the externally toothed member. An optical fiber is entrained between the toothed members and has one end exposed to a light source and the opposite end connected to a detector which is operable to detect changes in the intensity of the light transmitted through the fiber. As the bluff body vibrates, the toothed members are displaced relative to one another causing changes in the radius of curvature of the segments of the optical fiber received between the teeth, thus changing the intensity of light transmitted through the fiber in proportion to the changes in the radius of curvature.

Abstract: A data gathering system comprising a single optical fiber having one or more modulators formed thereon, means for launching into the fiber an interrogating light pulse which propagates in a first direction, means for generating at each modulator an optical return signal which propagates in the fiber in a second direction opposite the first direction and which has an intensity which is variable in response to variations in an external signal incident at the modulator, and means for detecting and processing each such return signal. The return signal comprises a portion of the interrogating light pulse which is coupled into the fiber in the second direction via evanescent coupling. The return signal from each modulator (or array of modulators) is identified via time division multiplexing. A signal processing means may be coupled to the fiber for generating a unique return signal from each of one or more modulator arrays, each array comprising a selected subset of the modulators.

Abstract: Dynamic behavior of structures subject to vibrations is monitored with light coupled into a single multi-mode optical fiber positioned within or on the structure. Vibration caused strain or deflections in the structure are detected by interference light signal intensity variations caused by differential phase changes in the transmission modes. These intensity variations are optically detected to provide an electrical output. Actuators may be positioned at the vibration nodes of the structure and energized by signals derived from the electrical output signals to suppress the vibrations.

Abstract: An optical fiber hydrophone system in which a single optical fiber is used for all of the acoustical sensors in the system. A signal source and detector provides an optical signal in selected form, such as continuous or pulsed and detects and extracts an identifiable output signal. Each sensor is in the form of a sensing portion of the single optical fiber. Each sensing portion includes two optical reflectors separated one from another by a predetermined length of said optical fiber. Variations in acoustical pressure incident on the sensing portion causes a change in the predetermined length. This causes reflected portions of the optical signal to interfere with one another. Such interference is detectable for extraction of the identifiable output signal. In one form each sensing portion has two terminal branches of a mechanically deformable material, deformable in response to the fluctuations in acoustical pressure.

Abstract: An acoustic sensor with ambient pressure and temperature compensation having a photoelastic element positioned between a diaphragm and a support beam. Thin layers of oil between the photoelastic material and both the diaphragm and support beam prevent surface stress of the photoelastic element due to slowly varying pressures while surface stresses are caused thereon by relatively rapid pressure variations.

Abstract: A pressure and temperature compensated acoustic transducer utilizing a pressure sensitive birefringent element coupled between a flexible diaphragm sealing the transducer and an internal variable rigid diaphragm that forms two internal chambers. Relatively rapid variation in pressure applied to the birefrigent element cause fluctuations in the phase difference between orthogonal components of a polarized light beam traversing the photo-elastic material. Detections of this phase difference variation provides signals representative of incident acoustic signals. Provision for the transfer of liquid filling the chambers permits the equalization between the two chambers of slowly varying internal pressures caused by changes in external ambient pressure and temperature.

Abstract: A device for measurement of vibrations comprises a microwave generator whose energy is transmitted through an antenna system to an object being investigated, reflected therefrom and fed to a detector through an antenna system, said detector also receiving energy of high-frequency reference oscillations. The antenna system comprises an elliptical mirror, in the first focal point of which, near the mirror, there is mounted a radiator irradiating the entire surface of said mirror, while the object being investigated is located in the immediate vicinity of the second focal point, which is remote from the mirror.

Abstract: A process control instrument, in which the resonant frequency of a vibrating string varies in accordance with changes in a process parameter being monitored, employs a pneumatic drive system to induce the string into oscillation. Pressurized gas is discharged through a port, such as a jet nozzle, which is disposed to allow the gas to impinge on the outer surface of the string. Variations in the alignment between the gas discharge port and the string permits different modes of vibration, one of which is particularly suitable for process measurement purposes. In a particular embodiment of the apparatus, an optical sensor detects the frequency of vibrations, resulting in an intrinsically safe instrument for use in explosive environments.

Abstract: A vibration sensor is formed by coupling the vibration to be sensed to change the positional relationship between grating means and light beams so that the resultant variations in light intensity of the beams beyond the grating means vary with a function of the sine and cosine of the positional change. This allows the detection of the vibrationover a wide range of frequencies and amplitudes.

Abstract: A vortex flowmeter including a single optical fiber into one end of which a light signal can be transmitted from a source to the other fiber end where it is vortex modulated. Modulated light at the other end is then reflected to a receiver back along the same optical fiber. Relative movement between the other fiber end and a reflector serves to modulate the light signal. Embodiments are disclosed in which the other fiber end moves and the reflector is stationary. In the alternative case, the other fiber end is stationary and the reflector moves.

Abstract: Apparatus is provided for detecting the presence of acoustic signals which includes a laser source, and a detector coupled to opposite end of an acousto-optic transducer. The transducer may employ fiber optic waveguides, etched to allow evanescent coupling therebetween, and disposed within a flexible housing. Integrated and planar optic transducers are provided in various forms employing two integrated optic waveguide channels, two planar waveguides, or a planar waveguide and absorber combination. Each configuration is disposed within a flexible housing and the waveguides are separated from each other by a predetermined distance. Any flexing of the housing is transformed into a displacement of the waveguides relative to one another. The coupling between the waveguides is a very sensitive function of distance, and hence detection of variations in the energy coupled by the waveguides provides an indication of the presence of the acoustic signals.

Abstract: A hydrophone remotely senses impinging acoustic energy. Light output from a laser is split and launched into a single-mode fiber which transmits it to an optical resonator at its end. The resonator is made up of a fixed fiber end having a dielectric coating and a movable mirror which is displaced in response to an incident acoustic signal. The acoustic signal displaces the mirror so that mirror movement modulates the intensity of the reflected beam which is transmitted back through the single-mode fiber and received at a detector. The frequency and magnitude of the reflected beam yield acoustic signal information.

Abstract: Sensing of acoustic waves is achieved by providing spaced apart stationary and cantilevered optic fibers whereby inertial forces created by acoustic signals modulate an optical signal carried by the fibers through vibration of the cantilevered fiber.

Abstract: Turbine blade vibration detection apparatus having two or more extremely narrow beam radar sensors positioned to direct their radar signals towards predetermined blade row or rows. A blade identification circuit is provided for each blade row having an associated radar sensor for providing an output count indicative of which blade is being examined by a particular radar sensor. The gating of the blade count and radar sensor signals is governed by a computer which performs a frequency analysis of the radar signals and compares the result with predetermined threshold values.

Abstract: A system for monitoring vibration or mechanical motion of equipment utilizing an optical waveguide sensor coupled to the equipment. The optical waveguide sensor is formed into a coil or a sinuous path which exceeds the bend radius or critical angle for internally reflected light directed through the waveguide. Vibration or mechanical force imparted to the waveguide from the equipment being monitored further alters the bending losses in the waveguide, and this change in bending losses is used to generate a signal as a function of the vibration or mechanical force.

Abstract: An optical technique for detecting acoustic waves of selected frequency and determining their angle of arrival in a medium such as water. The technique utilizes one or more lengths of single mode optical fiber having a birefringence whose orthogonal axes are helically disposed throughout the length of the fiber at a predetermined uniform pitch. Sound pressure waves of certain frequencies incident upon the fiber throughout its length change its birefringence which affects the relative phase of polarized light components propagating from one end to the other by an amount proportional to the amplitude of the acoustic wave. The twisted optical fiber may be arranged in parallel with other like fibers and axes twisted at different pitches thereby enabling detection of sound waves over a range of frequencies and their angles of incidence.

Abstract: In an apparatus for receiving ultrasonic waves by optical means a laser beam illuminates a workpiece surface at which ultrasonic waves are manifest in the form of cyclically occurring surface deformations. The reflected light is transmitted to an optical interferometer as a measuring light beam and the beam exiting from the interferometer is converted to an electrical signal and amplified to provide a measuring beam responsive electrical signal. A portion of the laser beam immediately before being incident on the workpiece surface is also passed through the interferometer as a comparison beam. The exiting comparison beam light is converted to an electrical signal, amplified and time delayed to provide a comparison beam responsive electrical signal. By means of a subtracting circuit the comparison beam responsive electrical signal is subtracted from the measuring beam responsive electrical signal to provide a difference signal which is evaluated.

Abstract: A light source is operated near its threshhold and its output is split and sent in opposite direction about a fiber optic coil which is exposed to acoustic energy. The recombined light out of the coil is modulated at acoustic frequency. The modulated light can be fed back to the light source which responds to the modulation with large amplitude variations which are sent to a detector for conversion into an electrical signal representative of the acoustic energy. Alternatively, the light beam may be directed from the fiber coil to the detector directly. The sensors can include components for rejecting noise at frequencies not of interest and a plurality of similar sensors can be formed in an array to obtain directional information or increased sensitivity.

Abstract: An optical system for frequency-modulation heterodyne detection of an acoustic pressure wave signal. An optical beam is directed into a Bragg cell outside of the fluid medium in which acoustic signals are to be detected. The Bragg cell modulates the incident beam such that two beams of different frequency exit the cell. The two beams are directed into an input optical fiber and the resultant combined beam is transmitted over a desired distance to a fiber optic transducer disposed in the fluid medium. The transducer includes two coiled optical fibers, a reference fiber and a signal fiber, each of which has a different sensitivity to incident acoustic pressure wave signals. The transmitted beam is directed from the input optical fiber through a power divider which splits the beam into two equal parts, one part passing through the reference fiber, the other part passing through the signal fiber. A filter in the signal fiber transmits only a fraction of the light at one of the two frequencies.

Abstract: When sensing the presence of ultrasonic energy in a workpiece portion by illuminating such portion with light from a single-mode frequency stabilized laser, the reflected light, frequency modulated by the Doppler effect due to the ultrasonic energy induced deflection of the workpiece portion, is passed through a gas filled light filter. The frequency modulated light is amplitude modulated by the filter by selecting the frequency of the laser to cause a point of operation which is located along a steep slope portion of the absorption curve characteristic of the filter. To increase the steepness of the slope portion of the filter, the present invention discloses the use of laser light to saturate the filter in a part region.

Abstract: A device for measuring vibration is herein disclosed and claimed, said device comprising: a vane attached to a vibratory member; a light supply and at least one detector; and light guides. The vane includes or is attached to a mask having therein a plurality of light directing and light opaque elements. During vibration the mask travels transversely of the light path. The elements of the mask may be encoded, as with a Gray Code, so as to yield both amplitude and phase information. Or the elements may be so arranged as to chop the light into a plurality of pulses for each vibration of the vane through the use of a second, stationary mask. In either case the device yields information whose interpretation is substantially independent of fluctuations in the intensity of the source light.

Abstract: A fiber optic sonar system wherein first and second optical fibers are wound on a common mandrel and provided with a light energy beam. An acoustic signal differentially varies the index of refraction of the optical fibers to result in an interference pattern dependent upon the frequency of the received acoustic signal or signals. The apparatus is operable to form one or more hollow conical receiver beams.

Abstract: An optical system which detects acoustical signals in a fluid medium such as seawater. The acoustical sensor assembly includes an acoustical sensor which is formed by two optical fibers which have different sensitivities to acoustical signals and are connected with the optical radiation conductor or conductors by use of an optical coupler which couples optical radiation into each of the optical fibers of the acoustical sensor. Since the optical fibers of the acoustical sensor have different acoustical sensitivities to acoustical signals, the phase of the optical radiation transmitted through each optical fiber of the acoustical sensor will change differently due to acoustical signals incident thereon. The optical radiation from the optical fibers of the acoustical sensor is directed back through an optical fiber to a photodetector. The photodetector produces a modulated output signal in accordance with the acoustical energy detected.

Abstract: A method and apparatus for sensing motion relies upon the total light traitted by an optical fiber. The fiber is wound in a spiral coil and cemented to a rigid base and a portion of the fiber's cladding is removed exposing its core. A highly refractive plate is placed closely adjacent the exposed core. When the plate is displaced, it intercepts at least a portion of the evanescent field that is adjacent to the spiral core. The intercepted portion reduces the total amount of light otherwise projected through the coiled optic fiber so that a detector can provide representations of the amplitude and frequency of the plate motion. The plate only penetrates the fiber's evanescent optical field which is associated with the total internal reflection at the glass-to-air interface at the fiber's surface. Adjusting devices and pressure compensation optionally are employed making this device suitable for use has a hydrophone.

Abstract: Disclosed is an apparatus and method for nondestructive testing of structures where the apparatus includes a transducer for generating an ultrasonic acoustic signal, a nonlinear medium for parametrically generating a special, ramp, waveform, and an acousto-optic broadband receiver for detecting a reflected signal from the test structure. A homodyne interferometer is provided to measure the change of refractive index of the acousto-optic receiver, and generates an electrical signal representative of the reflected acoustic signal. Signature analysis techniques are utilized to evaluate the reflected waveform to determine the characteristics of the structural defects.

Abstract: This invention relates to an optical fiber acoustical sensor for sensing acoustic vibrations and in combination with an incoherent or coherent source of light such as a LED or a laser and a photo detector to determine the frequency and amplitude of the sound pressure variations. The invention consists of an element of optical fiber without cladding surrounded by a liquid or plastic potting material permeable to sound pressure and having an index of refraction slightly less than the fiber. The intensity of a light beam transmitted by means of fiber optic waveguides, single or multi-mode, from a source of light through the sensor to a photo detector varies with the variation of sound pressure to which the sensor is subjected. If the sensor is in water, the transmitted light intensity varies with the acoustical pressure in the water because the changes in liquid or plastic index of refraction changes with the sound pressure.

Abstract: A device is provided for measuring the amplitude of vibration of a vibratory element. The vibratory element or reed has a vane attached to it extending between opposed fiber optics light guides. The vane has a mask portion which has slits forming alternating light-transmitting elements and opaque elements uniformly spaced in the direction of movement of the vane and lying in the path of light between the light guides. One of the light guides has a stationary mask with at least one slit corresponding in size and orientation to those of the vane. When light is transmitted from one of the light guides to the other while the vibratory member is vibrating, the light must pass through the slits of the masks and is alternately transmitted and cut off. By counting the number of minimum light transmissions, therefore, the amplitude of the vibration can be determined.

Abstract: An electro-mechanical transducer is disclosed for measuring physical parameters such as vibration, acceleration or the angular orientation of an object to which it is attached. A closed container partially filled with a fluid, has a light source and light detector mounted in optical communication with the container's interior. The arrangement of the detector and light source is such that light from the source must pass at least once through the surface (i.e., air-fluid interface) of the fluid before being detected. A constant incident light intensity is provided within the chamber and the resultant transmitted light is measured by the detector and an associated meter circuit. As the container is vibrated, or the angular relationship of the surface of the liquid with respect to the detected light rays is varied, the light transmissive and refractive properties of the liquid surface are altered, thereby altering the output of the light detector.

Abstract: The present invention relates generally to the utilization of laser interferometry for performing detection of buried structures such as underground natural gas pipeline. More specifically, the invention relates to the use of a laser interferometer system for detecting leaks and similar defects, such as corrosion, in buried pipelines, pressurized containers or other metallic structures, based upon the sensing of subnanometer earth surface displacements produced by elastic waves which are emanated from the leak or defect and propagate in the surrounding earth medium.

Abstract: A transducer that combines a noncontacting displacement probe with a self-contained target. The target is held in position against a vibrating surface by a housing which also supports the noncontacting probe. The target vibrates with the surface and the probe senses the vibrations of the target.

Abstract: To obtain a photographic record of an object surface having superimposed interference fringes arrayed as a function of the deformation which results in the object from an applied stress, which may be mechanical, thermal, or the like, the object is first illuminated with coherent light. The illuminated surface is then photographed with a camera having an optical wedge disposed over half of its lens to record two slightly displaced overlapping images of the object on the camera film. The object is then stressed by changing the ambient temperature or pressure or other mechanical loading, and the undeveloped film is exposed to a second set of overlapping images. The developed photograph contains a set of equal amplitude fringes representing the interference pattern between the two fringe sets generated by the two exposures and arrayed as a function of the strain in the object as a result of the stress.

Abstract: An electro-optic sensor including a cylindrical lens and a photosensitive diode array at the focal plane of the lens for measuring the angular displacement of a point light source from the neutral plane of the lens.In one application of the inventions the vibrational characteristics of an aircraft wing structure under load can be determined. A plurality of light emitters are judiciously scattered over the surface of the wing and the electro-optic sensor is attached to the fuselage. The emitters are sequentially energized and the readings of the sensor are synchronized with the emitters to provide the desired data. In other applications a pair of sensors will give two dimensional information and two pairs can be used to give three dimensional information.

Abstract: A receiver probe for ultrasonic energy is described in which the surface deformation caused by compressive wave energy affects a thin gas-filled gap, its width being in the order of 10.sup.-7 meter. The gap is formed by opposing surfaces of an optical prism and an optical interference means. A beam of light is conducted to the boundary surface between the prism and gas. Changes in reflected and/or transmitted light beam portions resulting from compressive wave energy induced changes in gap width are sensed by opto-electric means.

Abstract: Electro-optical gaging system has an electronic camera which develops a raw camera pulse having a width that approximates the dimension between edges of an object imaged on the camera. A camera pulse processor employs edge detecting techniques using raw pulse differentiators, threshold detectors, zero cross-over detectors, and an autocorrelator to eliminate differentiator-generated noise. This processor produces a precise output pulse that accurately defines the object edge dimension and may be used to drive A/D measuring and/or converting circuits.

Abstract: An instrument for measuring the amplitude of vibration of a vibrating object consists of a first optical system for periodically projecting the image of a grating onto the vibrating object and second optical system having an optical axis intersecting that of the first optical system in the vicinity of the object, for sharing the image projected on and reflected from the object and recording the shared image on a photographic film. The measurement of the amplitude is obtained in the form of a moire pattern.

Abstract: An electro-mechanical transducer is disclosed for measuring physical parameters such as vibration, acceleration or the angular orientation of an object to which it is attached. A closed container partially filled with a fluid, has a light source and light detector mounted in optical communication with the container's interior. The arrangement of the detector and light source is such that light from the source must pass at least once through the surface (i.e., air-fluid interface) of the fluid before being detected. A constant incident light intensity is provided within the chamber and the resultant transmitted light is measured by the detector and an associated meter circuit. As the container is vibrated, or the angular relationship of the surface of the liquid with respect to the detected light rays is varied, the light transmissive and refractive properties of the liquid surface are altered, thereby altering the output of the light detector.