Abstract: The present invention relates to an optical sensor of air borne acoustic waves. The sensor comprises means for producing mutually coherent optical sampling and reference beams, which may be combined to form an intermediate frequency carrier, the sampling beam being exposed to the acoustic field, in which acoustic wave induced density variations occur. These density variations produce a variation in the index of refraction and thereupon a phase modulation of the sampling beam. This phase modulation may be recovered by an optical detector and a phase detector as an electrical signal representative of the acoustic signal.
The invention has application to security systems.
May 19, 1986
Date of Patent:
March 30, 2004
Lockheed Martin Corporation
Joseph Lawrence Chovan, Martin Francis Lowry, Evelyn Hope Monsay, William Arthur Penn, William Pattee Whyland, Lawrence Richard Snowman
Abstract: An on-line scanning sensor system includes first and second horizontally extending guide members connected by side members to define a rigid box-like frame, and a support structure for suspending the box-like frame via vibration-absorbing devices such that vibrations are substantially attenuated before reaching the guide members. Further, the system includes a carriage mounted on the first guide member for scanning motion across a traveling web of sheet of material, and interferometer components mounted to the carriage for splitting and recombining infrared light and for directing a collimated beam of the recombined light onto the traveling sheet. Still further, the system includes a detector for receiving light from the interferometer components during scanning.
Abstract: An interferometric-based pressure transducer is fabricated from two layers of silicon having different crystal orientations which have been processed using selective anisotropic etching to produce in one silicon layer a mirror surface and a groove that is aligned with the mirror, and a pressure-responsive membrane in the other layer. The layers are joined with the membrane opposite the mirror, and an optical fiber is secured in the groove so that light from the optical fiber is conveyed by the mirror surface between the membrane and the optical fiber. Conventional interferometric apparatus compares transmitted and received light in order to sense deformation of the membrane and thereby sense pressure.
Abstract: A device for use in the testing of an optical probe which has at least one optical transmitter/receiver pair composed of one optical transmitter for emitting optical energy along a first path and one optical receiver for receiving optical energy propagated along a second path, the device including: a housing (4,6) formed to be mechanically coupled with the probe and having at least one pair of passages (14), with each passage (14) extending along a respective one of the first and second paths; and at least one optical energy reflecting member (18) disposed in the housing (4,6) and positioned relative to the passages (14) of the pair such that, when the housing (4,6) is coupled to the probe, light propagated along the first path from the transmitter is reflected by the reflecting member (18) into the second path toward the receiver.
Abstract: An interferometer for measuring the spherical accuracy of a surface to be measured in accordance with the light and dark distribution condition of interference fringes produced by the interference between a measuring light beam and a reference light beam. A part of the light from a light source is projected as a measuring light beam to a surface to be measured and its reflected light beam from the surface to be measured is superimposed on a reference light beam separately derived from the source light on a two-dimensional sensor. Arranged obliquely between the light source and the surface to be measured is a flat mirror formed therethrough with a pinhole for producing a spherical wave upon the passage of the light source therethrough. A spherical wave of light diffracted and emitted from the pinhole of the mirror is used as the measuring light beam. Also, the spherical wave produced by diffraction from the pinhole is also used for the reference light beam.
Abstract: Dynamic imaging microellipsometry (DIM) is a rapid full-field imaging technique for high resolution studies of thin-films. The DIM concept is based on radiometric polarizer, compensator, specimen, analyzer (PCSA) ellipsometry combined with video and image processing techniques. The theoretical basis for this approach is developed using the Jones vector and matrix formalism. Basic systems design is presented with error model predictions of ellipsometric accuracies better than 0.1.degree. for full-field .psi. and .DELTA. images captured in a few seconds with spatial resolution under 10 microns.
Abstract: A method for measuring refractive index of a thin film layer formed on the other layer having a known refractive index includes following steps. A step of irradiating P-polarized monochromatic light and S-polarized monochromatic light individually on the thin film layer with a prescribed angle of incidence, a step of determining reflections R.sub.p and R.sub.s for the P-polarized monochromatic light and S-polarized monochromatic light, respectively, by detecting luminous intensity of reflected light from the thin film layer, and a step of specifying the refractive index of the thin film layer by prescribed calculation either using the amount of phase changes produced by the reflection of said P-polarized light and S-polarized light on a boundary surface between the thin film layer and the medium, the phase changes being determined in accordance with the refractive index of the medium and the reflectances R.sub.
Abstract: An integrated optical device for measuring the refractive index of a fluid comprises a light guide formed on a substrate and having a guiding layer for carrying light beams, inserted between a lower layer and an upper layer having refractive indices below that of the guiding layer. The device includes an interaction measurement zone of the light guide for coming into contact with the fluid, the upper layer at the measurement zone having a thickness less than the penetration distance of the evanescent wave of the guided light beam. Outside the interaction zone, that upper layer has a thinckness greater than the penetration distance of the same evanescent beam. The device also has an interferometric optical system at least partly formed in the light guide and having a reference optical circuit and a measurement optical circuit including the measurement zone, for measuring the phase shift introduced by an effective index change of the guided mode due to the fluid.
Abstract: A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train.
Abstract: Disclosed is an optical apparatus which can be used for measuring displacement of an object. The apparatus includes an optical system for forming a linearly polarized beam whose polarization direction changes, a reflecting surface for reflecting the beam and for directing the beam in a predetermined direction, a photoelectric converter for photoelectrically converting a reflected beam directed in the predetermined direction, a polarizing device, arranged in an optical path of the reflected beam, for directing only a P-polarized beam or an S-polarized beam of the reflected beam toward the photoelectric converter.
Abstract: A displacement measuring apparatus comprises a scale relatively displaced to an irradiating beam, a reading head to read the scale by the irradiating beam, and control device to control the apparatus for avoiding substantially the leakage of the irradiating beam out of the apparatus in response to the positional error of the scale and the irradiating beam.
Abstract: A linear-and-angular measuring plane mirror interferometer measures two degrees of freedom, both linear translation and rotation angle, using a single interferometer optical assembly. In alternate orientations it can be used to measure either the pitch, roll or yaw angle. The linear-and-angular measuring interferometer splits the measurement beam at the interferometer optic, using a single integrated optical assembly to make measurements at two locations on a measuring mirror on a stage. In a first embodiment, the input beam is split, and two separate measurements, X and X', are made at two locations separated by a distance d. A second embodiment optically produces a direct measurement of X--X' at a detector. The input beam makes one interferometer measurement for X, then the polarization of part of the resulting output beam is rotated and the rotated part of the beam is returned for a second pass to make an interferometer measurement at a location offset by a distance d from the first pass measurement.
Abstract: A differential ellipsometer to measure the epitaxial growth of crystalization materials by molecular beam epitaxy. The ellipsometer projects a light beam (3) to the surface, and the reflected light beam (5) is returned to another point on the surface with the P and s linear polarization states interchanged. The output beam (7) from the further point is brought into interference with part of the incident beam for measurement or analysis.
October 31, 1989
Date of Patent:
October 29, 1991
c/o The Secretary, Comonwealth of Australia Department of Defence
Margaret A. Folkard, Richard H. Hartley
Abstract: A spatial heterodyne spectrometer has a two beam dispersive interferometer which includes a diffraction grating as a beam splitter/combiner. An incoming beam is collimated and passed to the grating in the interferometer where it is split into two beams which are recombined such that the angle between the wavefronts in the recombined beam at a particular wavelength is directly related to the deviation of that wavelength from a null wavelength at which the wavefronts are parallel. The recombined output beam is focused and imaged to produce Fizeau fringes across the output aperture, with these fringes being recorded on an imaging detector. The spatially varying intensity output of the imaging detector is Fourier transformed to yield an output indicative of the spectral frequency content of the image which is related to the wavelength content of the incoming beam from the source.
Abstract: A laser inteferometer system is disclosed which is able to make measurements of any deviations in the movement of a machine component which is moving along a main movement axis. The system can measure roll, pitch, yaw, straightness, and parallelism of two tracks using a single laser beam. FIG. 1 shows an arrangement for measuring roll of a vertical machine column (2) during movement of the column along the x-axis of a machine. A straight mirror (6) is positioned on the machine bed with its longitudinal axis aligned with the x-axis, and its reflecting surface normal to the x-axis. An optical component including a polarizing beam splitter is mounted for movement with the machine column and generates from a laser beam (A), a measuring beam (B1) and a reference beam (B2) both directed at the mirror, but laterally separated in the direction of the Z axis. The reflected beams from the mirror are re-combined in the optical device to form a return beam (C) directed towwards a detector adjacent the laser (9).
Abstract: Methods and apparatus for measuring the intensity of light scattered by particles suspended in a sample volume illuminated by an interrogating light beam directed along an input axis, utilizing plural Fourier optical systems having lenses arranged for illuminating multiple photodetectors. The lenses of each Fourier optical system can be of different optical powers, for providing low power and high power optical trains. A low power optical train provides high resolution measurements of light scattered within a small angular range at low angles relative to the input axis, while a high power optical train provides lower resolution measurements of light scattered within a larger angular range at higher angles.
March 3, 1989
Date of Patent:
October 15, 1991
Coulter Electronics of New England, Inc.
Steven E. Bott, Harry R. McKinley, W. Howard Hart
Abstract: A process for extracting long-equivalent wavelength interferometric information from a two-wavelength polychromatic or achromatic interferometer. The process comprises the steps of simultaneously recording a non-linear sum of two different frequency visible light interferograms on a high resolution film and then placing the developed film in an optical train for Fourier transformation, low pass spatial filtering and inverse transformation of the film image to produce low spatial frequency fringes corresponding to a long-equivalent wavelength interferogram. The recorded non-linear sum irradiance derived from the two-wavelength interferometer is obtained by controlling the exposure so that the average interferogram irradiance is set at either the noise level threshold or the saturation level threshold of the film.
Abstract: There is disclosed herein a cell assembly for a spectrophotometric analysis or detection of a substance within a small sample volume. The assembly includes a cell body with a small sample bore, along with windows engaging said body to allow radiation to pass through the sample bore and the windows. A sealing arrangement is provided for each window via a sealing washer which is loaded by two means. An inner portion of the sealing washer engages the window and is loaded by a first spring loaded assembly, such as a Belleville washer and plunger. An outer portion of the sealing washer is separately loaded by a ring pressed against the cell body.
Abstract: In a driving mechanism for driving an oscillating polarizer in a polarimeter, the polarizer is driven by a stepper motor which is controlled by a computer to make a reciprocating movement. A reference position sensor is connected to the oscillating polarizer, to provide a reference signal when the oscillating polarizer is in a determined position. A zero position of the reference position sensor is obtained by spacing the reference position sensor a predetermined number of steps of the stepper motor.
Abstract: A technoscope for checking for damage, especially a crack, in a surface of a cavity in a technical component, is arranged not only to establish the area of damage but also to measure the depth of a damaged area. To this end, the technoscope has a measuring attachment comprising a measuring probe with two electrodes for straddling the damaged area, and being supported in the cavity by a support element. The depth of the damaged area is measured by means of a depth measuring instrument sensitive to the disturbance of current flow between the electrodes, and the potential difference resulting therefrom.