Abstract: A method and apparatus for detecting through-hole voids in a multi-layer printed circuit board. The through-hole is formed with an electrical conductor for interconnecting wiring patterns of upper layers and wiring patterns of lower layers of the printed wiring board and is illuminated with a beam having a wavelength falling within a specified wavelength band capable of exciting an luminescent beam from a layer material. The layer material is exposed by a through-hole void in the through-hole of the printed wiring board. The luminescent beam excited by the illumination beam impinging upon the layer material by way of the through-hole void in the through-hole is focussed by means of a focussing optical system and a photoelectric converter. The photoelectric converter converts the luminescent beam into an electrical signal. The presence of a through-hole void is indicated by the electrical signal.

Abstract: An on-line method of and apparatus for inspecting an apertured mask sheet to be formed into a shadow mask for a color cathode ray tube are disclosed. In one of several embodiments described the mask sheet is linearly scanned by a laser spot transverse to the direction of advancement of the mask sheet. The peak values of the grey levels of the laser light transmitted by the mask sheet are detected and the data is convoluted electronically to form a series of convolution windows. The grey levels of the successively formed convolution windows are compared to at least one reference value and an output is produced at least in those cases where an error in the mask aperture size is detected.

Abstract: A pattern defect detecting system for an integrated semiconductor circuit or the like, utilizing the phenomenon that in the case of a test pattern having regularity, the intensity of diffracted light appearing on a back-focal plane of a lens is high, while defects or foreign matters not having regularity are low in the intensity of diffracted light. As a concrete example, an optical space modulator is used to record only an intense light portion in real time. The recorded diffraction pattern can be erased easily by, for example, application of voltage and radiation of light. A spatial filter can be prepared in real time in 1:1 correspondence to a test sample. Besides, even in the case of change of test pattern, an immediate action can be taken for continuous detection of defects, thus permitting test on-line.

Abstract: An optical double-balanced quadrature mixer for analysis of optical spectra, particularly asymmetric optical spectra. Beam splitting means are used in conjunction with a quarter wavelength retardation plate to enable highly stable, accurate and precise spectral analysis. The invention is illustrated in the context of a generic light scattering test setup.

Abstract: Apparatus for inspecting small bore ceramic laser tubes, which includes a support base with one or more support rollers. A fluorescent light tube is inserted within the laser tube and the laser tube is supported by the support rollers so that a gap is maintained between the laser tube and the fluorescent tube to enable rotation of the laser tube. In operation, the ceramic tube is illuminated from the inside by the fluorescent tube to facilitate visual inspection. Centering the tube around the axial light of the fluorescent tube provides information about straightness and wall thickness of the laser tube itself.

Abstract: Several photoelectric position measuring systems are described which utilize diffraction gratings to define the reference magnitude. Diffracted component beams are introduced by means of coupling-in gratings that have different grid constants from one another into optical waveguides to a coupler and there brought into interference. The interfering component beams are conducted from the outputs of the coupler via optical waveguides to detectors which transform them into electrical signals which are phase-shifted with respect to one another. Displacement of the diffraction grating is a measure for the position change to be measured of one machine component mounted for translation relative to another.

Abstract: Disclosed herein is an improved passive ring laser gyroscope with two systems: common mode and differential mode error systems. The common mode error system modulates counter propagating coherent radiation. The modulated light from a common source is split at a beam splitter before the reasonator cavity and then optically recombined at the same beam splitter for further propagation to an electronic detecting and demodulation servo system. The resulting electronic error signal is used to adjust the ring resonator and the laser so that the frequency output of the coherent radiation of the laser is substantially equal to the resonance frequency of the ring resonator. The differential mode error system optically substracts counter propagating radiation signals emanating from the resonator cavity to form a differential error signal that is detectable by an electronic detector for further processing by demodulation.

Abstract: A method of and an apparatus for detecting a fine foreign substance in which the surface of a specimen is illuminated with linearly-polarized laser beam to detect light scattered from the surface and having passed through a polarization filter, the back side of the specimen is illuminated with light from a light source such as a mercury lamp to obtain the light and darkness information or phase information on the specimen surface by transmitted light from the specimen, and fine massive and filmy foreign substances on the specimen surface are detected on the basis of information given by the scattered light and transmitted light.

Abstract: A method and apparatus for calibrating absolute and relative measurements of modulation and/or demodulation transfer characteristics of electro-optical and opto-electrical devices during setup of a lightwave component measurement system for characterizing performance of fiber optic systems and associated components. The lightwave component measurement system calibrated in accordance with the method of the invention provides the capability to measure the optical, electrical, and, especially, the electro-optical (E/O) and opto-electrical (O/E) components with specified measurement performance. In accordance with the calibration method of the invention, when the lightwave component measurement system is used to characterize an E/O or O/E device, an initial calibration reference is established based on the known characteristics of a lightwave source and lightwave receiver included in the lightwave component measurement system.

Abstract: A phase locked passive ring resonator gyroscope comprising a fixed frequency reference signal generator (Fm); a single piece body having laser and passive resonator cavities; a laser means using the laser resonator cavity responsive to a laser control signal from a laser servo for providing a single frequency light source (F0) for frequency modulating the single frequency light source to form a light source (F0) and having respective upper and lower side bands at frequencies F0+Fm and at F0-Fm; first and second voltage controlled oscillator means responsive to respective first and second control signal for frequency shifting the first and second frequency modulated ray center frequencies by a first and second variable offset frequencies to form a propagating and counterpropagating light sources; the second resonator cavity being a passive high Q evacuated cavity; a detector means for detecting a first offset frequency error signal and for detecting a second offset frequency error signal; cavity servo means re

Abstract: The interferometer comprises an emitter arm (10) excited by a source (11) and a receiver arm (20) associated with a photodetector (21) united by an optical coupler (50) so as to form a reference arm (30) and a measurement arm (40) terminating in a sensor (41). The arms (30) and (40) are constituted by one and the same optical fiber whose diopter of its free end (31) acts as a partially transparent mirror for the reference optical wave. This end (31) is coupled to the sensor (41) which returns the measurement optical wave through said diopter. Application in particular in the measurement of temperatures, for example in turbo-machines or of fluctuations of flow density.

Abstract: An arrangement for testing a reflecting surface of a solid body, especially a relatively complex reflecting surface such as that of a grazing hyperboloid, for deviations of its actual shape from its ideal shape includes a laser source and a positive cylindrical lens interposed between the laser source and the reflecting surface to be tested. The lens optically modifies the laser beam in such a manner as to propagate between the lens and the reflecting surface substantially normal to the reflecting surface and to be reflected from the latter for propagation back to and through the lens toward the laser source as a return laser beam having a wave front indicative of the actual shape of the reflecting surface and any aberrations of the lens. The arrangement further includes an interferometer that forms an interference pattern between the original and return laser beams, and a circuitry for evaluating the interference pattern.

Abstract: A solid state fiber optical semiconductor ring laser gyro apparatus with nonoptical readout which contains an optical fiber optically coupled with a optical amplifier diode which has a ground electrode and a plurality of non ground electrodes, which are both electrically and spacially separated and disposed across the optically active channel of the optical amplifier diode, the magnitude and direction of rotation of the optical fiber ring can be determined by examining the differences in phase information between the outputs on the plurality of non ground electrodes.

Abstract: An optically phase-locked electronic speckle pattern interferometer mixes a local oscillator beam with a beam reflected from a target surface to create a speckle pattern at each of two separate image planes. The speckle pattern includes speckles whose intensities vary as a result of time-varying Doppler shifting of the reflected beam by movement or deformation of the target surface. The local oscillator beam is phase-locked to the Doppler signature of a lock-point speckle on one image plane. The phase-locking of the local oscillator beam to Doppler information of interest enables the interferometer to coherently detect speckle in the image plane sharing frequency, amplitude, and phase characteristics with the lock-point speckle, which supports the efficient processing of images obtained from the other image plane. The processing produces a contoured image of the target surface, with demarcation between coherently and non-coherently detected speckle.

Abstract: An optical heterodyne measuring apparatus for effecting measurement of a subject, based on a phase difference and a frequency difference between a reference beat beam consisting of two laser beams having different frequencies, and a measuring beat beam which consists of the reference beat beam reflected by the subject. The apparatus includes a light source device for producing a first reference beat beam having a first beat frequency, and a second reference beat beam having a second beat frequence which is lower than the first beat frequency, a beat frequency detecting device, and a phase difference detecting device. The beat frequency detecting device detects a beat frequency between the first beat frequency of the first reference beat beam, and a beat frequency of a first measuring beat beam which consists of the first reference beat beam reflected by the subject.

Abstract: An apparatus to compensate for refraction of radiation passing through a curved wall of an article is provided. The apparatus of a preferred embodiment is particularly advantageous for use in arc tube discharge diagnostics. The apparatus of the preferred embodiment includes means for pre-refracting radiation on a predetermined path by an amount equal and inverse to refraction which occurs when radiation passes through a first wall of the arc tube such that, when the radiation passes through the first wall of the arc tube and into the cavity thereof, the radiation passes through the cavity approximately on the predetermined path; means for releasably holding the article such that the radiation passes through the cavity thereof; and means for post-refracting radiation emerging from a point of the arc tube opposite its point of entry by an amount equal and inverse to refraction which occurs when radiation emerges from the arc tube.

Abstract: An optical non-contact detection of profile errors of a surface or surfaces of an article, such as an industrial product is carried out by a coherent signal bea of light introduced along an imaginary plane and projected onto the surface of the article at a large angle of incidence. The signal beam of light is reflected from the surface toward the same imaginary plane and traveled past optical system toward a photosensitive material on which a separate reference beam of light is projected. A hologram of the surface is formed on the photosensitive material, which is used for an analysis of the profile errors of the surface.

Abstract: The surveying instrument contains a component part (1) for the optical imaging of a target and a camera (2) for the electronic acquisition of the image produced in the optical instrument part. A reference mark (20) is located in the optical part (1) of the instrument, and this is outside that region of this instrument part through which the optical axis passes. The image of the target is projected into the region located within the reference mark. Connected to the camera is a circuit arrangement which can detect both the effective center of the image of the reference mark and the effective center of the image of the target and which can determine not only the length, but also the direction of the distance between the two effective centers. The surveying of an object or a region can be carried out automatically by means of this instrument.

Abstract: The operating point of a fiber optic rotation sensor is to obtain an increased sensitivity in the measurement of the Sagnac phase shift between counterpropagating beams in a sensing loop. The two counterpropagating optical waves are mixed for detecting interference of the waves to indicate the phase difference between them. The phase of the waves is modulated in accordance with a periodic function having a frequency equal to f.sub.s =(2n+1)/2.tau. where .tau. is the transit time for an optical wave in the sensing loop. The interference pattern of the two waves is periodically sampled at a frequency equal to the modulation frequency.

Abstract: Provided herein is a ring laser gyro system having a special and improved partially transparent output mirror which provides relatively undistorted circularly polarized coherent light beams to the photo detector and amplifier of the system from the laser cavity thereof. This improved mirror achieves its results by sandwiching a non-quarterwave stack between two quarterwave stacks of multi layer, all of which are coated on a Zerodur substate mirror. The improved mirror achieves nearly Zero phase retardation and a Tp/Ts ratio equal to one.