Abstract: A method and apparatus, utilizing multiple light signals, for extending the dynamic range of an interferometric system such as an optical fiber gyroscope based on dual wavelength measurement of the Sagnac phase shift in order to determine the fringe number of the interferometric fiber system, thereby increasing the unambiguous range of the device. An analogue measure of the fringe number is provided, thus eliminating the need for digital fringe counting or tracking. An apparatus is described for measuring absolutely, within certain upper bounds determined by the exact wavelengths used, the rotation rate when the system is powered up in a rotating frame.

Abstract: For generating several interferograms which differ from each other in the relative phase position between the interfering partial beams, a light source is utilized having a coherence length less than the optical path difference between the two component beams in the measuring path of the interferometer. Furthermore, at least one optical delay device is provided which splits the beam into two component beams and which generates an optical path difference between these component beams which is approximately the same as the optical path difference of the partial beams in the measuring path of the interferometer. Thereafter, the delay device again unites the component beams congruently.

Abstract: An improved fiber-optic inertial sensor of the Sagnac interferometer type is provided with the capablility of precise linear measurement of sensed motion. The sensor uses closed-loop synchronous demodulation of sensed signals representative of angular motion in a manner that permits operation over a wide dynamic range in inertial rate along with null stability and a high degree of noise rejection.

Abstract: An interferometer is provided for producing an interference pattern from light such as laser light which travels along first and second optical paths and at the end of each such path there is a respective fixed mirror for directing light to a common optical path. Means are provided to vary the optical path length of light in the or each first or second optical path to produce an interference pattern in the common optical path, which means comprises a pair of parallel-plane optical flats in accordance with one embodiment of the invention, which are each rotated in an oscillating manner to produce a linearly varying optical path length during rotation. According to another aspect of the invention first detector means are provided for detecting a reference part of the interference pattern produced to derive therefrom a reference signal, and second detector means are provided for receiving the interference pattern to thereby derive signals indicative of successive parts of the interference pattern.

Abstract: Two electrically isolated photodetectors are responsive to an interference pattern output of a ring laser angular rate sensor. The two photodetectors are constructed to have a periodic pattern of photosensitive zones. The photodetectors are positioned such that the periodic pattern is selectively oriented relative to the interference pattern fringes so as to produce a pair of output signals out of phase with each other in the presence of rotation.

Abstract: An optical nondestructive testing method of composite materials utilizes optical interferometry to find the resonant vibration from at least one surface of the target part of an object being inspected, and also determines the resonant frequency at that time. Another resonant frequency exhibiting the same resonant vibration is then obtained from the rear surface of the part of the object being inspected and the two resonant frequencies are used to derive the depth of defects in the object.

Abstract: A method and corresponding device, are provided for detecting the propagation time variations in the ring of an interferometer and includes phase modulation of the contrarotating waves travelling through the ring by means of assymetric square waves at a period twice the initial propagation time, which create level zero phase shift stretches in the modulation of the difference between the two waves emerging from the ring. These level stretches result in pulses in the detected output signal whose width is variable with the propagation time. The invention applies particularly to the control of the wave length of the source of the interferometer, particularly with respect to temperature variations of the source.

Abstract: In a closed loop fiber optic gyroscope, the counter-propagating lightwaves are phase modulated by a triangular wave modulation with the triangular wave skewed to lock the phase difference between the counter-propagating waves alternately to specific values of phase difference which are greater than and less than the phase difference due to rotation. The difference in elapsed time between the up-slope and down-slope portions of the triangular wave modulation yields a measure of rotation angle, whereas such difference in elapsed time divided by total elapsed time yields a measure of rotation rate. The phase difference is further modulated about the locked values at a higher frequency, such higher frequency phase difference modulation being synchronously detected to produce a rotation rate signal component employed to generate the skewed triangular wave. Various other features are employed to light polarization errors.

Abstract: A spectrum modulation encoding sensor subjected to the physical magnitude to be measured is connected by an optical fiber to a source of incoherent light, and by an optical fiber to a static demodulation system comprising a set of birefringent elements producing a birefringence gradient along a privileged optical direction x; the system demodulates the signal provided by the sensor optically by means of a Fourier transform.

Abstract: A novel method and apparatus for determining the accuracy of artwork produced from a laser direct imaging system employs a calibration substrate which has images of opposed, perpendicular scales and registration marks thereon. The overall system dimensional error is determined directly from substrate measurements, as is the magnitude of the mechanical and processing errors.

Abstract: An apparatus for optically detecting the attachment state of extraneous matters to a translucent shield member. The optically detecting apparatus comprises a light-emitting unit having a plurality of light-emitting elements each emitting a light ray toward the translucent shield member, a photoelectric transducer unit having a plurality of transducer elements each receiving each of the light rays reflected on the translucent shield member, and a data processing unit coupled to the transducer unit. The transducer unit generates detection signals corresponding to the quantities of the received light rays and the data processing unit successively compares the level of each of the detection signals with a predetermined level to produce binary signals in accordance with the results of the comparison so that a binary signal pattern is defined at the respective transducer elements.

Abstract: Glassware inspection apparatus comprises a first light emitting diode position to illuminate a first region of the ware, a first driver for driving the first light emitting diode in a first modulated mode, a first photodetector positioned for receiving light of the first light emitting diode which illuminates the first region of the container, and a first demodulator for the output of the first photodetector. The apparatus also comprises a second light emitting diode positioned to illuminate a second region of the container, a driver for driving the second light emitting diode in a second modulated mode, a second photodetector positioned for receiving light of the second light emitting diode which illuminates the second region of the container, and a second demodulator for the output of the second photodetector. The two modulation modes minimize cross-talk between the first and second light emitting diodes.

Abstract: Discloses a mirror chip and mirror assembly for ring laser angular rate sensors. A mirror assembly utilizes a silicon substrate upon which is deposited in mirror material. The silicon substrate is then affixed to a second substrate by a thermally sealable bonding agent.

Abstract: A phase modulation type fiber optic gyroscope having a greatly improved output stability without a large increase in the number of basic components of the gyroscope system. In accordance with the invention, the d.c. component of the output of a light detecting element which provides the two circulating beams is sensed and employed to control the output of the light-emitting element so as to be constant.

Abstract: In a precision ring laser gyroscope, to eliminate the effect of an unwanted and unintentional moment generated as a result of a force being applied onto a pathlength controller, a pathlength control assembly is constructed to have optimal hub and diaphragm portions such that the mirror element mounted thereto does not tilt in response to the unintentional moment.

Abstract: The phase of light passing through an optical waveguide is modulated by aying electric current to heat the waveguide and thereby alter the length and refractive index thereof. An application for the thermal phase modulation concept is provided in a Mach-Zehnder interferometer.

Abstract: A light dot reticle rifle shooting sight has tubular lens and battery housings supported in parallel for movement from right-handed to left-handed shooter positions by 90 degree rotation of a circumferential groove on the lens housing relative to a pin projecting into the groove from a mounting strap. Elevation and windage adjustments of the light dot are provided by adjustment screws that pivot a lens tube against diametrically opposed rubber biasing cushions and a coaxial position restoring force of a rubber ring fulcrum through which the tube extends. Rotation of the sight from right- to left-handed position interchanges the elevation and windage adjustment functions of the screws.

Abstract: An optical frequency analyzer for measuring an optical frequency spectrum with high accuracy, high resolving power and high stability by heterodyne detecting the incident light with the aid of a local oscillator, wherein the local oscillator comprises an optical frequency synthesizer/sweeper or a marker signal attached tunable laser. The optical frequency analyzer can be modified to measure the incident light itself as the object of measurement or light emerging from the object of measurement can be the incident light.

Abstract: A quadrupole-wound sensing coil for a fiber optic gyroscope and a method for forming such a coil. Layer pairs wound from two supply reels terminate with three concentric turns adjacent distinct home flanges. The concentric turns form borders at the ends of the wound layers and bridges to new layers to be formed so that fiber pinching and undesirable microbends are avoided while packing density is enhanced.

Abstract: An optical electronic method for the measuring of a workpiece is disclosed. A beam of radiation is used to illuminate an edge of the object to be measured to form an actual diffraction pattern. The actual diffraction pattern is converted to electronic signals by means of a sensor and correlated electronically with a predetermined theoretically calculated diffraction pattern.