Showing papers on "Collimated light published in 1977"

Laser diode collimation optics

Abstract: The present invention related to optical collimating systems and has particular reference to beam compression of laser diode emission

Speckle elimination by random spatial phase modulation

Abstract: A process and apparatus for improving image creation in a coherent light imagery system which involves directing diffused laser light onto a mirror having a rocking motion that will cause the reflected rays to sweep a two-dimensional area and focusing the reflected light through a diffuser before collimating same for use in image creation. More particularly, this invention creates the rocking motion by applying a combination of voltages to three independent piezo-electric crystals upon which the mirror is mounted.

Chirped gratings in integrated optics

Abstract: Gratings with variable periods (chirped gratings) have been fabricated by recording the interference pattern of a collimated laser beam with a converging beam generated by a cylindrical lens. An analysis is presented for the behavior of the chirped gratings as a function of wavelength, the angle between the illuminating beams, the F number of the lens, and its position. To calculate the power radiated into air, the coupled-mode equations are solved for the case of a waveguide with chirped surface corrugation. Experimentally, chirped gratings have been etched on the surface of an optical waveguide and used to couple light out of the waveguide. It was found that the light was focused outside the waveguide, and the fraction of the power radiated into air compared favorably with the theoretical calculation. The focal point outside the waveguide was found to move by about 1 cm when the wavelength was changed by 500 A-in agreement with theoretical estimates.

Laser–ion coaxial beams spectrometer

Abstract: An apparatus has been constructed to provide laser excitation of ion beams in both coaxial and crossed configurations. The coaxial geometry provides very high sensitivity and nearly Doppler‐free wavelength resolution for spectroscopic measurements, and allows the use of the Doppler shift to ’’tune’’ the wavelength. A novel transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis. The ion beam is highly collimated and a high‐resolution 180° electrostatic analyzer is used for photofragment energy analysis. The apparatus has demonstrated a resolution of better than 10 meV for normal photofragment spectroscopy and 0.001 meV for coaxial beams photofragment spectroscopy using a single‐mode laser. While providing these high resolutions the apparatus has an overall sensitivity several orders of magnitude greater than conventional ones.

Laser beam divergence utilizing a lateral shearing interferometer

Abstract: An analysis of the lateral shearing interferometer is given for laser beams. The results enable a simple determination of the local radius of curvature of the wavefront. In addition, the presence of phase distortion in the beam may be ascertained.

Evenly illuminated display devices

Abstract: The molecules in a twisted nematic liquid crystal are, in general, skewed relative to the optical axis of the cell (the perpendicular to the plane surfaces defining the boundaries of the crystal cell), and their birefringent effect on plane polarized light varies asymmetrically for such light making varying angles with the optical axis of the cell. When the cell is positioned between crossed polarizers and the cell is energized so that light is supposed to be completely extinguished, some rays are nevertheless transmitted so that the transmitted intensities at different viewing angles vary. To avoid this resulting variation of intensity with viewing angle, the cell is illuminated from behind with collimated light (i.e., all rays parallel to the optical axis of the cell) so that all rays "see" the average molecular director in the same way; a solid catadroptric element is utilized to both collimate the light and achieve essentially constant luminous flux intensity upon the display. To restore a reasonably wide angle of view, a diffuser is positioned in front of the display. The invention may be used with any type of display device which has a transmission characteristic which varies with the angle of rays passing therethrough.

System and method of fluorescence polarimetry

Abstract: A system and method for measurement of the polarization of fluorescence A laser source provides a collimated linearly polarized beam of high intensity and small cross-section A relatively small number of optical components are employed to minimize spurious fluorescence and spurious polarization which usually occurs from most optical materials A photodetector provides an electrical signal in response to and representative of fluorescence polarization and is processed to directly produce first and second signals representing the difference and sum components of the polarization equation, the ratio of these components being directly provided without need for division computation

Nonstationary two-level resonance fluorescence

Abstract: Analytic expressions are obtained for the spectrum of the light scattered when a collimated atomic beam is illuminated at right angles to its path by a CW monochromatic laser beam tuned to resonance with a two-level transition. The spectra vary depending on the portion of the interaction region from which the scattered light emanates. The spectrum of the light from a finite sub-region of the interaction volume is described as a function of the location and length of the sub-region, and of the intensity and frequency of the laser. Several interesting features related to the turn-on of the interaction as well as to the finite observation interval are found.

Two dimensional light beam selection system

Abstract: A position selection system comprising a map of a plurality of selection positions arranged in columns and rows with a normally unenergized light emitter and a respective normally disabled light detector positioned at opposie ends of each of the columns and rows. The light emitters are sequentially energized and the respective light detectors are synchronously sequentially enabled to thereby avoid the necessity of collimating light from the light emitters.

Polarization-Dependent Absorption of Laser Radiation Incident on Dense-Plasma Planar Targets

Abstract: Polarization-dependent absorption of obliquely incident laser radiation by dense plasmas has been observed. Irradiation of a planar plasma with a nearly collimated $p$-polarized laser beam shows an enhancement in absorption by a factor of 2 to 2.5 over $s$-polarized irradiation. Theoretical estimates of the effect of resonance absorption under the present conditions show agreemwnt with the experimentally observed results.

The early detection of osteoporosis by Compton gamma ray spectroscopy.

Abstract: The density of the distal end of the radius is one of the parameters used to determine the presence and degree of osteoporosis in patients. The bone density has been determined by measuring the intensity of Compton scattered photons, since this is proportional to the absolute density of the scatterer, in materials for which Z/A is constant. A collimated beam from a 500 mCi 137Cs source was used and the intensity of the scattered radiation measured at an angle of 90 degrees . The exact point of measurement was determined by a two-dimensional scanning technique. A plastic water phantom was used to calculate the correction needed for absorption and backscatter by the surrounding tissue.

Optical system for rotating mirror line scanning apparatus

Abstract: This optical system permits larger tolerances in mirror facet pitch angles for rotating mirror line scanning apparatus without the use of expensive lenses having toroidal and like complex surfaces or lenses employing elements that have one cylindrical surface whose center of curvature lies on or very near the axis of the scanned surface. A lens system having a negative cylindrical element with its axis perpendicular to the plane of deflection is employed in a rotating mirror scanning arrangement. The lens system images the rotating mirror surface on the scan line in an azimuth perpendicular to the plane of deflection of the beam while ringing the collimated rays of the light source in the plane of deflection of the beam to focus in the one scan line.

Highly collimated broadside emission from room‐temperature GaAs distributed Bragg reflector lasers

Abstract: Highly collimated laser beams have been observed to be coupled out by second‐order Bragg scattering from GaAs distributed Bragg reflector lasers. The beams are perpendicular to the waveguide plane and have an angular width of less than 1°. The diodes have a separate confinement structure and operate at room temperature with thresholds as low as 1.4 kA/cm2.

Laser gauge for measuring changes in the surface contour of a moving part

Abstract: A gauge for measuring small changes in the contour of the surface of a moving part, such as a rotating cylinder or sliding flat surface, as the part passes a point, using a monochromatic source of coherent light is disclosed. The gauge is based on the fact that the size and rate of movement of the speckles of a speckle pattern (formed by coherent light focused onto a nonspecular moving surface) vary in accordance with whether or not the beam is actually focused on the surface. In the preferred form of the present invention, an expanded and collimated laser beam is focused by a focusing lens onto the surface of the moving part. The speckle pattern light reflected by the moving surface is received by one or more photodetectors. The photodetectors develop pulses at a rate determined by the rate of speckle movement. These pulses are applied to a signal processor that counts them, if they are above a predetermined level. Pulse counts are made over predetermined time periods; and, if speckle size, as well as speckle rate is used as the measurements basis, only pulses occurring simultaneously on the outputs of two photodetectors are counted. The pulse counts made during adjacent time periods are analyzed by a signal processor and, then, compared. The results of the comparisons are used to control the focusing lens such that the coherent beam is brought to, and maintained in, focus on the surface of the part. Focus exists when the pulse count is maintained at a maximum level. The focusing lens position is denoted by an indicating scale mechanism, which provides the displacement information needed to determine the size of changes in the contour of the surface that cause refocusing of the focusing lens.

Generation of a parallel X-ray beam and its use for testing collimators

Abstract: A technique is described, by which a glass strip may be bent to match any curve of large radius of curvature, to a high degree of accuracy, so that it may be used as a glancing incidence X-ray or extreme ultraviolet optical element. The desired match is obtained by applying the optimum combination of end couples and by varying the cross-sectional moment of inertia along the length of the strip. A particular case, that of a parabola for use as a laboratory X-ray collimator, is considered in detail. The analysis predicts that a collimation of one or two arc seconds should be obtainable in practice, with simple and inexpensive apparatus. A prototype collimator to be used for the testing of space payloads using geometric (McGrath) collimators is described and laboratory results presented.

Laser rangefinder with calibration device - has sliding bridge triple mirror directs either send or receive beams to detector

Abstract: The laser rangefinder with alignment adjuster comprises a laser generator (2) with optical system and a receiving optical system (5) with a detector (4). The receiver consists of a collimating telescope, a fixed triple mirror reference device and an adjustable triple-mirror. The adjustable reflector directs light into the receiver collimator lens either from the telescope or from the transmitting optics by shifting the reflector from one position to the other. The detector comprises a pair of prisms (8, 9) with dichroic filter (10) between their mated surfaces, cross-hairs and optical viewer (11). The beam-splitting prisms also direct light to the photo-multiplier or video detection device (19).

Lateral shifts of totally reflected gaussian beams

Abstract: At an interface with incidence-angle-dependent reflection coefficient, a highly collimated totally reflected beam experiences a displacement of the beam axis and the phase center from the location predicted by geometrical optics. Studies in the literature of the lateral (longitudinal and transverse) beam shift have produced conflicting results. Here, the shift phenomenon for gaussian beams is analyzed by a rigorous method whereby the high-frequency point source or line source Green's function solution as expressed in ray-optical terms is converted into the beam solution by assigning a complex value to the source coordinates. Results obtained for two-dimensional and three-dimensional electromagnetic fields at plane isotropic and anisotropic interfaces are compared critically with those found elsewhere. Also included are the lateral shifts at a curved cylindrical boundary, which have not been studied heretofore. These planar and curved geometries are relevant, respectively, to beam coupling into slab and fiber waveguides. Our expressions for the beam shifts are consistent with those required for correct conversion of multiply-reflected rays or beams in slabs and fibers into guided modes, thereby lending further support to the arguments presented.

Glue drop detector

Abstract: This invention relates to a method and apparatus for determining whether a glue drop is present on the reflective inner surface of a closure. Collimated light is projected onto the reflective inner surface of the closure, and a measurement is taken of the amount of light which remains collimated after reflection from the closure. The measurement of the amount of light reflected in this way is used to determine whether a glue drop is present.

Testing opaque workpieces, particularly tiny or thin elongated objects such as pins, bolts, wires, or the like, for orientation, size and material integrity

Abstract: A light source, preferably an electrical flash tube, generates a beam of light which, preferably, is collimated to provide a parallel beam output. The workpieces are placed in the beam of light to generate a shadow image. The shadow image and surrounding beam portions are projected on a screen, with intervening optical enlargement, on which photoelectric sensors are located positioned in the projected shadow image and preferably also in adjacent regions of the light beam, the outputs from the sensors being compared with each other, or with a reference, to determine relative shadow image characteristics of regions of the objects in the light beam path, the output signals being a measure of differences in characteristics, and hence determinative of orientation, size, or integrity of the workpiece material. To test for size or orientation, two sensors are located at the end portions of the shadow images of pins, or bolts, carried through a test path interposed between the parallel beams from the light source, before enlargement.

Optical system for changing the cross sectional dimensions of a collimated beam of light

Abstract: An optical system for providing changes in the cross sectional dimensions of a substantially collimated monochromatic beam of light directed along an input path of the system in relation to the dimensions thereof along the output path of the system. For example, either increasing or decreasing the beam diameter of a laser source of radiant energy is representative of an area of usefulness.

Interferometric measuring system

Abstract: In an interferometric measuring system, a collimated monochromatic and coherent beam of light (1, I1 -In)impinges on a grating 1 disposed parallel to the test surface 2. It has been found that in the above arrangement, a diffraction order (preferably the first diffraction order S1 -S4) of the light reflected from the face of the grating opposite to the test surface is always parallel to three diffraction orders of the radiation which after being first diffracted upon its first passage through the grating and reflected from the test surface is again diffracted upon its second passage through the grating. These four radiations (S1 to S4) generate two interference fields, the combination of which generates a beat pattern. According to the invention, the angle of incidence of the radiation impinging onto the face of the grating opposite to the test surface is chosen in such a way (preferably from 0.5° to 5°) that the areas in which the beat patterns generate an additional field of interference fringes, related to λ/4 distances, from the test surface are a maximum. When properly selecting pairs of angles of incidence and of distances between test surface and grating the resolution of the resulting fringe pattern (interference fringes symmetrically interleaved by beat fringes) is improved by the factor of 2, i.e. the distance between two fringes is related to a λ/4 distance from the test surface, as opposed to the interferometric methods known heretofore where the maximum resolution is defined by fringe distances related to λ/2 distances from the test surface.

High speed computerized tomography imaging system

Abstract: A high speed tomographic x-ray imaging system comprises an array of x-ray sources disposed opposite a closely spaced array of x-ray detectors. Small groups of sources in the array are simultaneously pulsed to provide x-ray transmission data along a number of ray paths through a body undergoing examination. X-ray energy from each source in the array is collimated to illuminate only a small sector of the detector array. High speed, unambiguous x-ray transmission information, is thereby produced.

Fiber optic coupler with concave spherical reflecting elements

Abstract: An optical coupler transfers light energy signals relative to an optical h which includes a fiber optic cable. A body member includes first and second ports at opposite ends for supporting first and second terminals of the fiber optic cable in laterally offset alignment relative to each other. First and second reflective elements, preferably of concave spherical configuration, are supported within the body member for collecting and reflecting light energy transmitted through the first and second terminals of the fiber optic cable. The first and second reflective elements are so configured and positioned as to transmit collimated light energy between them for completing the optical path between the first and second terminals of the fiber optic cable. First and second planar reflective surfaces are supported from opposite sides of the body member to intercept a portion of the path of the collimated light energy and are angularly disposed to laterally transfer light energy relative to the optical path between the first and second reflective elements. Preferably, the planar reflector surfaces are removable so as to minimize interference with light energy signal transmission between the collimating reflective elements and reduce attenuation. Additionally, the planar reflector surface may desirably be frequency sensitive so as to extract from or introduce into the optical path only certain selected frequencies of light energy signals.

Azimuth monitoring system

Abstract: A system for monitoring changes in azimuth due to shifts in geological features of the earth's surface, using a collimated laser beam which is split and reflected from a plane mirror and a prismatic mirror to target area showing translational and rotational changes in the mirrors location. The beam is directed to a second pair of mirrors at an angle to the beam which will verify the location movement, source or target.

High resolution laser fluorescence spectroscopy in the deep blue spectral region

Abstract: High-resolution laser spectroscopy measurements have been performed in the wavelength region around 4000 A using a pulsed dye laser acting on a collimated atomic beam. Extra-cavity Fabry-Perot filtering was used to achieve a narrow line-width of the laser light. Isotope shifts were measured in the 4216 A and 4202 A rubidium lines with the result Δσ(87, 85)=124.3(4)MHz, andΔσ(87, 85) = 124.2(7)MHz, respectively, and in the 3988 A ytterbium line with the resultδσ(176, 174)=−509(4)MHz, Δσ(174, 172)=−530(4) MHz.

Boresight method and apparatus

Abstract: In a system employing a collimated beam projector radiating energy of a single wavelength and an image detector sensitive to a band of wavelengths, a boresight technique includes the steps of extracting a portion of the projected beam, focusing the extracted portion onto a predetermined point of a boresight target material until said material responsively emits radiation in said band of wavelengths, and collimating the emitted radiation into said image detector at a field of view location corresponding to the projected beam location.

Collimating solar radiation collector

Abstract: This invention describes an improved solar energy collector which passively concentrates the rays of the sun. The collector comprises a transparent cover which collimates incident rays of light and directs such collimated sunlight towards an absorbing target wherein the radiation's energy is received and utilized. The transparent collector cover consists of a lamination of transparent plastic or glass elements. Sunlight incident on the cover over a range of angles is reflected internally between the sides of the elements. These elements are so shaped that internal reflections result in the sunlight becoming collimated. Specifically, the elements are curved so that the horizontal distance between the sides of adjacent elements remains constant whereas the length of a normal between the sides increases along the path of incident light. The effect of these apparently diverging surfaces is to cause each subsequent internal reflection at a particular internal surface to occur at a successively lower angle of incidence, thus tending to collimate the light's rays. The resulting collimated rays are then reflected upon leaving the bottom of the collector cover in such a way that they are directed towards the absorbing target.

Autocollimating assembly for the self-calibration of a stellar navigational system

Abstract: An autocollimating assembly is provided for the tracking or position-sensing sub-system of a stellar navigational system, the sub-system being mounted on the stable platform of an inertial measuring unit. The autocollimating assembly, in conjunction with mirrors mounted on the internal surface of the spherical case of the inertial measuring unit permits accelerometer bias, scale factor and alignment measurements to be made, as well as gyro drift and alignment measurements, and sensor alignment for scale factor measurements, with the sub-system installed in the space vehicle. The autocollimating assembly of the invention includes a pattern of point light sources which generate a plurality of light beams which are collimated by the lens system of the sub-system, the beams being reflected back from one of the mirrors on the internal surface of the case of the inertial measuring unit. The reflected light is focused onto the surface of the vidicon or solid state stellar sensor in the sub-system. The angle θ of the mirror can be measured by the linear displacement of the light image on the sensor surface from its nominal position.