Abstract: Incorrectly assembled circuit boards become detected by directing interfering laser beams on the surface of a circuit board. Fringe patterns develop on the surfaces of electronic elements as well as the board proper. These fringe patterns are compared with those of a reference standard and anomalies become electronically detected.

Abstract: In a particle measuring instrument for measuring particles entrained in liquids, a gear pump located downstream from the flow cell of the particle measuring instrument is used to maintain a constant rate of flow through the flow cell. When the source of liquid is at a high pressure, a pressure regulator and a check valve are used to maintain the pressures at the inlet and outlet sides of the gear pump, respectively, at predetermined pressure values to maintain a predetermined pressure differential across the gear pump. When the source of liquid to be measured is at ambient pressure, the outlet of the gear pump is connected to ambient pressure and the gear pump draws liquid through the flow cell causing the pressure at the inlet side of the gear pump to drop the predetermined pressure differential below ambient pressure.

Abstract: A sensor unit of an optical probe includes an illuminating device having an illuminating point arranged on the central portion of a detective surface facing a to-be-measured object, and eight light receiving devices arranged on the x and y axes in the detective surface, for receiving a reflected light from the object, four light receiving points among those of the eight light receiving devices being symmetrically arranged on the x axis with respect to the illuminating point and the remaining four light receiving points thereof being symmetrically arranged on the y axis with respect to the illuminating point. The rotation angle .theta. of the unit normal vector around the x axis and the rotation angle .phi. thereof around the y axis in the detective surface are calculated by processing the amounts of light received by the eight light receiving devices of the sensor unit.

Abstract: An apparatus for the determination of the wavelength and the detection of velength shifts in wavelength-encoded fiber sensors, such as Bragg grating sensors. The apparatus is implemented in fiber and uses a pair of tuned fiber gratings to provide a filter type function that tracks the wavelength component of a signal from a wavelength-encoded sensor.

Abstract: A dual-wavelength absorption detector is provided. The detector includes an electronics section, a three branched optical guide and a detector-cell. Each branch of the optical guide has a plurality of fibers, and at one end the branches are separated and connected to different portions of the electronics section. Two of the three branches are terminated next to LEDs having different wavelengths, a measuring wavelength and a reference wavelength. The third branch is terminated next to a photodetector. At the opposite end of the optical guide the three branches are combined to form a common end which is terminated within the detector-cell. The detector-cell includes a continuous-flow sample cell connected to a sample line. Within the detector-cell, the common end's fiber ends are held at a fixed location on one side of the sample cell with a concave mirror being located on the opposite side.

Abstract: A wide range straightness measuring system of the present invention accurately determines lateral and angular displacement of a probe carriage of a cartesian robot. The system includes a laser aligned with an x-axis rail of the cartesian robot system which generates a laser beam having two polarization components. A pentaprism beamsplitter is disposed on an x-axis carriage aligned with the laser. The beamsplitter orthogonally splits the laser beam into an x-axis reference beam and a y-axis reference beam. An x-axis interferometer receives the x-axis reference beam and determines a relative position value of the probe carriage measured along the x-axis. A y-axis interferometer receives the y-axis reference beam and determines a relative position value for the probe carriage measured along the y-axis. A beam monitor receives a polarized multiplexed output of the y-axis interferometer and monitors the lateral shift of the energy centroids of the beam polarization components.

Abstract: A method and an apparatus for measuring a very small displacement of an object. The first and second beat signals are produced by light beams of different frequencies diffracted by a diffraction grating. The phase difference between the first and second beat signals is detected, thereby measuring the relative displacement of the diffraction grating.

Abstract: An air refractometer measures the refractive index of air by directing a laser beam onto a first nonlinear optical crystal to convert a part thereof into a second-harmonic wave, directs the laser beam and the second-harmonic wave onto a reflecting mirror which reflects them onto a second nonlinear optical crystal to convert another part of the laser beam into a second-harmonic wave, produces interference fringes by interference between the harmonic wave produced by the first nonlinear optical crystal and the harmonic wave produced by the second nonlinear optical crystal, counts the number of interference fringes generated when the reflecting mirror is moved, and divides the number of interference fringes by the distance moved by the reflecting mirror.

Abstract: An object is projected through the lens system to be corrected to the image plane where the position of the diffraction limited ideal image is readily ascertainable. At least one primary image defect or Seidel Aberration is measured. These aberrations include distortion, curvature of field or Petzval curvature, spherical aberration, coma, and astigmatism. Interferometry is one technique typically used to measure the aberrations of the system. Based on the measurements, the location of an apparent object is computed. The apparent object is an imaginary location of the object which would cause the image of the object to register to the diffraction limited ideal image. Although only one corrector plate may be required to achieve the desired optical system performance improvements, in the preferred embodiment at least two corrector plate mounting planes are designed and mounts made for the insertion of first and second corrector plates to correct beam convergence and focus to the ideal image.

Abstract: For the detection of the presence of contaminants in yarn a first optical sensor is used to measure the amount of light reflected from the yarn. The signal from this sensor not only depends on the presence of contaminants but also on the diameter of the yarn. For eliminating the dependence on the yarn's diameter, a second signal is recorded, which depends essentially only on the yarn's diameter. By appropriate combination of these two signals in a microprocessor system the influence of the yarn's diameter in the first signal can be eliminated.

Abstract: Fiber optic interferometric sensors and methods of manufacturing same are disclosed. These sensors comprise a unitary substrate having a channel therein and an axis extending through the channel. The unitary substrate also comprises a reflective surface extending in a plane perpendicular to the axis. An optical fiber having a terminated surface thereon is also provided. The optical fiber extends axially within the channel and is arranged so that the terminated surface and the reflective surface are movable relative to one another in response to a phenomenon to be sensed. The unitary substrate also comprises positioning means integral therewith for positioning the optical fiber within the channel. The method of manufacturing the fiber optic interferometric sensors comprise the steps of providing a unitary substrate and forming a channel therein so that an axis extends therethrough.

Abstract: A mobile laboratory for in situ detection of organic and heavy metal pollutants in ground water is disclosed. Pulsed laser energy is delivered via fiber optic media to create a laser spark on a remotely located analysis sample, which is irradiated. In a first operational mode, laser energy emitted from an optical delivery system, e.g., a fiber optic media, is focused, for example by one or more lenses, on the surface of an analysis sample, thus generating a plasma. At high temperatures generated by the laser spark, dissociation occurs, allowing the emitted spectrum to be analyzed for the presence of trace elements, such as heavy metals. Because temperature changes after the end of the laser pulse result in a changing spectral characteristic of the sample, signals emitted from the recombining plasma can be used to identify the contents of the sample.

Abstract: Disclosed herein is an interferometric surface inspection machine which is arranged to facilitate the inspection of finished spherical lens surfaces, and which essentially includes: a surface plate formed with a through light guide opening in a predetermined position; an up-down guide means suspended from the lower side of the surface plate; an interferometer liftably supported on the up-down guide means and having a reference lens with a reference surface thereof disposed on the side of the light guide opening and in face to face relation with said light guide opening; and a lens mount portion adjustably located in a predetermined position above the light guide opening in the surface plate and adapted to support peripheral edge portions of a spherical lens element on the side of the lens surface to be inspected.

Abstract: By using a non-linear guided wave optical time domain reflectometry (OTDR) technique, specific features of an optoelectronic integrated device may be probed by detecting the reflections and back-scattering of a short light pulse along a waveguide interconnect. An integrated optical correlator in the form of a second harmonic generation (SHG) waveguide and a photodetector array detects and measures ultra-short pulses for optical ranging. Used with a standard CCD camera, the direct images of the autocorrelation of compressed Nd-Yag pulses (FWHM of 5 ps) have been monitored at video rates. Used with a cooled CCD camera for OTDR, reflections from samples have been observed with an interfeature resolution of about 0.15 mm in GaAs, limited by the FWHM of the laser pulses. Appropriate signal processing can increase the positioning resolution to better than 50 .mu.m. Additional applications are demonstrated, including the monitoring of fiber lengths (to within 30 .mu.m in real time) and temperature sensing.

Abstract: For the detection of contaminants, a yarn or a thread is led through a zone of measurement, which is formed as a flat slit in an optically transparent body. This transparent body has outer surfaces for diffusely or non-diffusely reflecting light back into the body. Light is led into the body from several sources of light, such that the yarn is diffusely illuminated from all sides. The sources of light are arranged and adjusted such that the brightness of the yarn detected by a sensor is equal to the brightness of the yarn's background field. In this way, the measurement becomes independent of the yarn's thickness. Due to the use of a flat slit for receiving the yarn, the yarn can be inserted into the zone of measurement by the same procedures as they are used in conventional yarn cleaners.

Abstract: An accelerometer or seismometer has an elastic disk bearing a mass distributed peripherally around the disk. The disk is supported for flexure and for isolation from mounting strain by a stob centrally through the disk. The accelerometer or seismometer has a pair of flat spirals of optical fiber, each spiral being fixedly attached to a corresponding disk side so that disk flexure lengthens a spiral on one disk side and shortens a spiral on an oppositely facing disk side and so that temperature differences between the spirals are minimized. The pair of spirals are connected as legs of a fiber optic interferometer so that the interferometer provides an output corresponding to the flexure. Several of the disks and asociated pairs of spirals may be coaxially mounted to provide increased sensitivity.

Abstract: A system for sensing a measurand field, the system comprising a source of broadband light, a sensor, an unbalanced optical interferometric apparatus, and a signal processor. The sensor produces an optical return signal having a wavelength functionally dependent on the measurand field. The interferometric apparatus produces an electrical interference output signal having a phase shift functionally dependent on the wavelength of the return signal, and the processor develops a processing signal indicative of the measurand field value.

Abstract: A technique for aligning corresponding features on opposite surfaces of a transparent substrate. In one embodiment thereof a laser beam is applied to a pair of grating elements on one surface of the substrate to produce an interference fringe pattern on the opposite surface, the centerline between the grating elements being at a known distance from the features on the one surface and corresponding to the center bright space of the fringe pattern. A reference mark on a movable mask, which reference mark is at the same known distance from feature locations on the mask, is aligned with the center bright space of the interference fringe pattern and the feature locations on the mask can then be used to position features on the opposite surface which are aligned with the features on the one surface of the substrate.

Abstract: Apparatus and process are disclosed for calibrating measurements of the phase of the polarization of a polarized beam and the angle of the polarized optical beam's major axis of polarization at a diagnostic point with measurements of the same parameters at a point of interest along the polarized beam path prior to the diagnostic point. The process is carried out by measuring the phase angle of the polarization of the beam and angle of the major axis at the point of interest, using a rotatable polarizer and a detector, and then measuring these parameters again at a diagnostic point where a compensation apparatus, including a partial polarizer, which may comprise a stack of glass plates, is disposed normal to the beam path between a rotatable polarizer and a detector. The partial polarizer is then rotated both normal to the beam path and around the axis of the beam path until the detected phase of the beam polarization equals the phase measured at the point of interest.

Abstract: An interferometer Fourier transform spectrometer, having increased speed, is capable of performing a Fourier transform in parallel, in analog form, using a weighted matrix. The spectrometer includes a linear detector array responsive to an interferogram. The detector array is coupled to a plurality of integrating sampling amplifiers. Each column of a group of columns of the matrix is coupled in parallel to a respective integrating sampling amplifier, and the output signals from each row of a group of rows form an output signal array.