Showing papers on "Collimated light published in 1978"

Quantum beats from nuclei excited by synchrotron pulses

Abstract: Synchrotron pulses will excite low-lying nuclear levels whose subsequent decay will exhibit beats with frequencies equal to the nuclear hyperfine splittings. The highly collimated pulses incident on very small enriched single crystals at a Bragg angle will result in an appreciable fraction of the incident radiation in the spectral width of the nuclear resonance being coherently scattered into a highly collimated beam which will exhibit beats corresponding to the difference frequencies emitted by different nuclei, and a decay parameter $\ensuremath{\Gamma}$, with marked time dependence.

Laser beam level instrument

Abstract: A lightweight, portable laser beam level instrument has an optical path which includes a solid state light source; a pendulous, positive lens; a rotatable pentaprism or mirror equivalent; and a glass plate which is tilted to provide fine tuning. The level instrument also includes a damping mechanism, a waterproof enclosure and a clip-in battery pack. The solid state light source is a diode in a specific embodiment and produces an intense beam of rapidly diverging infrared laser light. The postiive lens is suspended below the diode at approximately the focal length of the lens from the diode to collimate the light. The pendulous suspension lens maintains the beam in a truly vertical position with respect to the earth to provide self-leveling in a limited range of movement of the instrument. The pentaprism or equivalent converts this vertical beam to a horizontal beam. The glass plate is positioned between the diode and the lens and can be tilted in two orthogonal degrees of adjustment to provide a fine tuning for optical centering of the diode and the lens. Oscillation of the pendulous lens is damped by magnetic or air damping.

Collimated radiation apparatus

Abstract: Apparatus for exposing an object to x-ray radiation including adjustable object supporting and compressing means and first collimator means having an opening and being disposed between the x-ray generator and the object supporting means. Second collimator means having an opening and being disposed between the object supporting means and x-ray detecting means. Means are provided for moving the first and second collimator means in such fashion as to maintain alignment between the openings therein and the x-ray generator, in order to sequentially expose portions of the object of x-ray passing through the first collimator means and permit such x-ray to pass through the opening in a second collimator means and impinge upon the x-ray detecting means. The object supporting and compressing means is preferably structurally independent of the collimator means. The x-ray detecting means preferably takes the form of a highly sensitive detector such as a film-screen cassette or a self-scanning array of photodiodes optically coupled to scintillator means.

Split-pulse laser method for measuring attenuation coefficients of transparent liquids: application to deionized filtered water in the visible region

Abstract: Attenuation coefficients α(λ) for collimated quasi-monochromatic radiation passing through deionized filtered water were measured throughout the 418.6–640.3-nm wavelength region by use of a split-pulse laser method, which employs reference and sample cells arranged in a geometry similar to that of a Michelson interferometer. The radiant source was a pulsed wavelength-tunable dye laser possessing a relatively short coherence time. This paper includes descriptions of theoretical and experimental techniques applicable to the split-pulse laser method and includes a tabulation of α(λ) measured for deionized filtered water at 26.4 ± 1.7°C.

Laser beam expander

Abstract: An inexpensive laser beam expander including a first mirror system comprising an off axis section of a Schwarzschild telescope system with a first, convex spherical mirror and a second, concave spherical mirror, having a first common center of curvature, the input laser beam being incident on the first mirror and reflected therefrom to the second mirror, the second mirror forming a real image at a first image point; and a second mirror system comprising a backwards Schwarzschild telescope system including a third, convex mirror and a fourth, concave mirror, having a second common center of curvature, the second system being such that parallel incident light striking the fourth concave mirror and reflected to the third convex mirror will form a virtual image behind the third convex mirror at a second image point, the second system disposed so that the second image point coincides with the first image point whereby the third convex mirror intersects the light reflected from the second concave mirror and reflects it to the fourth concave mirror, the fourth concave mirror providing a collimated output beam which is expanded.

Pulse generating apparatus

Abstract: A three-channel optical shaft angle encoder has two channels for encoding the incremental angle and the direction of rotation of a shaft. A third channel provides a synchronizing index pulse for encoding the absolute position of the shaft once per revolution. The encoder has an emitter module containing three high irradiance LED emitters and integral truncated collimating lenses for producing three closely spaced collimated light beams, one beam for each channel. These light beams are modulated as a function of the relative angle between a code wheel coupled to the shaft and a phase plate fixedly mounted to the body of the encoder. The modulated light beams are received by a detector module having beam splitting truncated and siamesed lenses positioned to split each of the closely spaced light beams and to focus each of the split beams onto a photo detector pair. The photo diode pairs are coupled to balanced hysteretic optical comparators which provide analog and digital output in response to the position and direction of rotation of the shaft.

Amplitude modulation of light beam

Abstract: An optical modulator suitable for use with a collimated light beam having a moderate cross section and a fast response time and operational at relatively low voltage includes, for example, a glass prism and a smooth metal surface that are separated by an adjustable gap. The gap is filled with a medium, for example, air, having an index of refraction lower than the prism. A beam of monochromatic light is passed into the prism at a specific angle of incidence to undergo total internal reflection at the glass prism-gap interface. A change of approximately 1 micron in the thickness of the gap is sufficient to change the reflectivity from greater than 95% to essentially zero. The size of the gap is mechanically adjusted and this mechanical device determines the frequency response of the light modulation.

Compact, rugged sensor for optical measurement of the size of particles suspended in a fluid

Abstract: A compact, rugged sensor for use in the measurement of particle sizes in a fluid stream is disclosed. The sensor permits the use of a light emitting diode as a light source by mounting a high grade optical system with its focal point at the point light source provided by the light emitting diode to collimate the generated light. This collimated light passes through an aperture formed in one dimension by the width of the fluid flow stream and formed in a second perpendicular dimension by a narrow transparent slit in an otherwise opaque shield adjacent the fluid flow stream. The collimated light source, together with the use of the flow stream as a light path boundary, substantially increases the accuracy of the sensor. All of this is accomplished in conjunction with a solid state light emitting diode source which permits the sensor to be used in shock and vibration environments which would have prohibited particle measurement using prior art sensors.

Ion beam generator having concentrically arranged frustoconical accelerating grids

Abstract: A grid system for an ion beam generator is provided having a frustoconical shape so that the collimated ion beam converges at a predetermined angle toward the target to provide selective beveled etching.

Optical measuring system

Abstract: Automatic test equipment for determining the optical properties of a test object is described. A highly collimated test beam of approximately one millimeter diameter is directed through the test object, is reflected, and passes through the test object a second time. The test beam source may be a laser and spatial filter, or equivalent. The reflected beam intensity and the exit point and return slope angle at which this beam leaves the test object are accurately measured to determine the optical characteristics of the test object. In one described embodiment, the exit point is determined by moving a knife edge to a point where half the light is blocked. The angle is determined by focusing the reflected beam and determining the position of the focal point, i.e. image height, by means of a pinhole mounted on a three axis micrometer platform. The light transmitted through the pinhole is detected by a light sensitive diode or equivalent. The entrance point of the test beam is determined by a mirror driven by a micrometer. A computer may be used to automatically drive all the micrometer scans and print out a numerical analysis of the optical properties of the test object. A second embodiment requires the test object to be located two focal lengths from an off-axis paraboloid mirror. A pinhole is located at the focal plane to determine the slope and a means for determining the beam position is located at the conjugate plane to measure the height of the exit beam. The second embodiment is more easily automated since the image height can be measured directly by any one of several electrical devices.

Optical measuring system

Abstract: A non-contacting optical probe incorporates an optical system designed to measure distances between various surfaces which may be internal or external such as exists in molds and the like. A collimated light beam is passed off-center through a first lens and focused to a first point on a first surface coplanar with the focal plane of the lens. When the distance between the first surface and the optical probe carrying the collimated beam changes so that a second surface is presented, this second surface is no longer in the focal plane with the result that a laterally displaced image of the point of interception of the collimated beam with the point of the intersection of the optical axis of the system occurs. This lateral displacement is imaged back through the optical system to a sensing surface. The primary focusing lens is then physically shifted along its optical axis to bring the focal plane into coplanar relationship with the second surface, the amount of lens movement being readily determined when the laterally displaced image point on the sensor surface is brought into coincidence with the center optical axis of the lens system on the sensor surface. The distance through which the lens is physically moved then corresponds precisely to the distance between the first and second surfaces.

Variable power attenuator for light beams

Abstract: An improved variable light beam power attenuator which uses a flat mirror d a focusing mirror fixed in a suitably movable structure. Linear movement of this structure varies the diameter of a spot of light illuminating a "diffraction-limited" aperture of a special shape. A second focusing mirror is provided to collect the "diffraction-limited" light transmitted by the aperture and to focus or collimate it. A second flat mirror may be used to re-direct the output beam. The mounting arrangement of the first two mirrors relative to the input light beam and the remainder of the power attenuator permit an all mirror system which requires only a single linear motion to change the power level of the transmitted beam. The use of an all-mirror system allows all the advantages of reflective optics over transmitting optics for high power CW (continuous wave) laser beam.

Simplified optical path-averaged rain gauge.

Abstract: It has previously been shown that the scintillations produced by raindrops falling through a collimated laser beam can be used to measure the drop-size distribution and the rainfall rate, both averaged over the path. We now present a theoretical analysis, verified by observation, showing that the variance of the scintillations detected by a line-detector measured at frequencies near 1 kHz is closely related to rain rate and is nearly independent of drop-size distribution. If only rain rate is desired, the variance type of optical rain gauge has several advantages over the earlier model. It could use a diverging beam, thus eliminating the practical difficulties of maintaining adjustment and pointing of a collimated beam. Furthermore, it is less sensitive to the presence of updrafts and downdrafts along the beam and can thus be used over rough terrain.

Interior measurement of enclosed spaces

Abstract: An apparatus for measuring interior profiles of enclosed spaces such as railway tunnels through optical means, achieves greater speed and precision than hitherto known apparatus by using a continuous collimated band of light together with means for maintaining the light band at a constant angle of incidence with the profile to be measured and means for detecting variations of the vertical angle of the light source while the light source and an associated image analyser are moved through the enclosed space

Reference light beam projector

Abstract: A reference light beam projector of the type which produces a modulated plane of light for use as a reference in many different applications such as for aligning railroad tracks. This modulated reference plane is formed by projecting a collimated light beam along a predetermined path and providing means for variably refracting the beam so to effectively variably bend the beam back and forth along a plane. Specifically, the means for variably refracting the beam is a rotating optical element comprising a window through which the beam is transmitted and variably refracted as the optical element is rotated.

Optical instrument for measurement of particle size distributions

Abstract: A method for measurement of the size distribution of particles suspended in a gas or in a liquid. The particle suspension is illuminated by a collimated beam of nearly monochromatic light. Part of the light scattered by the particles is collected by a lens and is passed through a spatial filter placed in the focal plane of the lens. The light transmitted by the filter is measured by a photodetector. The photodetector output is measured as different spatial filters are switched in place. A computer, microprocessor, or analog device acts on the measured values and produces the particle size distribution as an output. The data reduction algorithm consists of a linear transformation of the measured data vector, followed by the construction of a linear combination of basis functions for the size distribution. The spatial filters consist of transparencies with non-uniform transmittance functions. The average scattering angle is not restricted, but for broad polydisperse particle distributions near back scatter is preferred, in order to avoid an ill-conditioned data reduction problem. One of the spatial filters has a uniform transmittance for the purpose of background light subtraction, and to provide a bias in order to allow effectively indefinite filter transmittance functions.

Influence of the diffraction size of the transmitting aperture and of the turbulence spectrum on the intensity fluctuations of laser radiation

Abstract: The Huygens–Fresnel principle is used in an investigation of the influence of the diffraction size of the transmitting aperture and internal turbulence scale on the variance of the intensity fluctuations of laser radiation traveling in a turbulent atmosphere. The asymptotic formulas for the relative variance are derived for weak and strong fluctuations in a collimated beam whose transmitting aperture has the Fresnel number satisfying the condition Ω≥1; corresponding formulas are obtained also for a focused beam and a spherical wave. An analysis is made allowing for the deviation of the turbulence spectrum from the power law in the dissipation range. In the case of strong fluctuations the asymptotic behavior of the variance of a spatially confined beam differs fundamentally from the behavior in the case of unbounded (plane and spherical) waves if the coherence radius of the field is much less than the internal turbulence scale. In this case the relative variance reaches saturation at unity for plane and spherical waves, whereas for a confined beam the saturation level is higher and it is governed by internal turbulence scale as well as by the Fresnel number of the transmitting aperture.

Lensless method of measuring Gaussian laser beam divergence.

Abstract: The radii of a Gaussian laser beam was measured using a technique employing a CaF/sub 2/ attenuator and polaroid film. (AIP).

Lidar beam direction measurement by opto-electronic method - is by dividing quadrant detector difference voltages by summed voltages

Abstract: An opto-electronic measurement arrangement for the direction of transmission of a laser detector of light scattering particles, or lidar enables unambiguous noise immune measurement of the direction to an accuracy better than 10-4 using direct electro-optical techniques. The scatter trace image of the laser source (10) transmitted beam in the earth's atmosphere is formed on a quadrant detector using a receiver telescope and associated optical system. The deviation of the beam from being parallel with the telescope optical axis is derived by dividing the difference voltages between individual quadrants by the sum of the individual quadrant voltages. The stopped collimated beam is split. One partial beam is fed to the receiver detector and the other via an interference filter and focussing lens to the quadrant detector.

Stability Limits for Frequency Standards Using Divergent Beams

Abstract: A theoretical analysis is given of the stabilities obtainable with Rabi and Ramsey interrogation methods in divergent beams. The performances of both techniques in frequency standard applications are strongly degraded by first order Doppler effect when the divergence is such that the beam width becomes comparable with the transition wavelength. Upper limits exist for the stability obtainable in both configurations, with given beam intensity and detection efficiency, and for the frequency at which that maximum is reachable in mechanically collimated beams. Non-mechanical collimation (e.g. saturated absorption) should be used in order to reach that maximum at higher frequencies. Doppler-free interrogation methods appear to be the only way to remove these upper limits.

Prismatic light beam expander or compressor means

Abstract: A light optic data handling system for providing changes in the cross sectional dimension of a substantially collimated monochromatic beam of light by allowing the beam to be directed repeatedly, at Brewster's angle, toward and incident upon a common air/light conducting material interface so as to provide said changes utilizing a minimum of bulk material and space while achieving a very high degree of efficiency in the transmission of light through the system.

X-ray Replication of Masks by Synchrotron Radiation of INS-ES

Abstract: Synchrotron radiation has been used for X-ray lithography. At an electron energy of 1. 1 GeV, o.4 µm gold layer on 3 µm silicon membrane was sufficient for obtaining good contrast in PMMA for direct SOR total beam. By using the mask of the gold grating pattern with 692 nm period made by holographic method, the grating pattern with a large height-to-width ratio of very narrow line (2.2 µm: 0.2 µm) is obtained in PMMA. This result clearly demonstrates the high collimation of X-ray beam from the synchrotron. Effects of diffraction are observed in replicated patterns when a mask and a wafer are separated and are well explained by the theory of Fresnel diffraction as a function of the slit width, the wavelength and the distance between a mask and a wafer.

Laser scanning reprographic appts. - performs analysis and synthesis scans in alternation with common laser deflected from opposing sides of mirror drum

Abstract: A scanning electro-optical copying appts. uses a laser which emits a beam of coherent light which passes an acoustic optic modulator (2). A collimator (3) narrows the beam to a dia. corresp. to the analysis resolution required for the original document scanning. A bi-route deviator (4) alternately directs the collimated beam to the upper or lower sides of a frusto pyramidal mirror drum (5) driven by a motor (6). The beam thus performs alternative analysis and synthesis scans across respective ones of an original (7) and copy medium (8) fed in direction (F1, F2) orthogonal to the scan paths.

Method and apparatus for testing prescription glasses and other dual lenses optical devices

Abstract: A method of and apparatus for testing the optical axis of an optic device having respective left and right lenses. The apparatus is designed to simulate respective left and right axes of vision which intersect at a focal point lying on a central axis of the optical device. Two collimated light beams such as are produced by a laser are projected to pass through respective equally spaced points, lying on opposing sides of the central axis, with a distance spanning therebetween and intersecting at the focal point. The distance spanning between the spaced points is the interpupiliary distance measurement pertaining to a particular set of prescribed measurements. The apparatus includes supporting structure for retaining an optic device made according to the set of prescribed measurements. The supporting structure positions the optic device in a position normal to the central axis. An optic device which has been properly made will allow the two light beams to intersect at the focal point when positioned upon the supportive structure.

Optical system for creating high-intensity solar light beam

Abstract: An optical system concentrates solar light energy or energy from another light or electromagnetic radiation source into a low-diverging, collimated, high-intensity beam. The optical system includes an objective lens, an input collimating lens, a fresnel-like reflecting surface, a parabolic reflector, a pinhole aperture, and output collimating lens.