Showing papers on "Collimated light published in 1988"

Shaping of arbitrary dose distributions by dynamic multileaf collimation.

Abstract: Traditionally, the shaping of non-uniform dose distributions has been performed by using wedges or compensating filters. The advent of high resolution multileaf collimators may largely eliminate the need for material attenuators for modification of the beam. This is achieved by a new technique for the shaping of arbitrary dose distributions by dynamic motion of the collimator leaves. By employing narrow elementary slit beams that correspond to the smallest possible opening of the multileaf collimator, the optimal density of such slit beams, i.e. opening density, can be determined automatically using a newly developed inversion algorithm. The present method has two major advantages (1) internal structures in the field can be created, controlled solely by steering the collimator leaves, (2) the opening density determined by the algorithm never gives rise to underdosage: this is important from a radiobiological point of view.

Coherent addition of AlGaAs lasers using microlenses and diffractive coupling

Abstract: A near single‐lobed far‐field pattern was obtained from coherent operation of a nonevanescently coupled AlGaAs laser diode array. A diffractive microlens array collimated the individual beams to approximate a plane wave, and diffractive coupling from an external cavity mirror provided mutual coherence. A diffraction‐limited far‐field pattern was observed with 82% of the power contained in the central lobe. The method is directly applicable to two‐dimensional laser arrays and can be implemented as a single thin optical element.

Diffraction of atoms by a transmission grating.

Abstract: We have demonstrated a novel diffraction grating for atoms. A collimated beam of sodium atoms with a de Broglie wavelength of 17 pm was diffracted by transmission through an array of slits with a spatial period of 0.2 \ensuremath{\mu}m formed in a gold membrane. This is the first reported diffraction of atoms by a fabricated periodic structure. Our transmission grating for atoms can divide or recombine an atomic beam coherently, and may provide the easiest route to the realization of an atom wave interferometer.

Bright output optical system with tapered bundle

Abstract: An optical system producing bright light output for optical pumping, communications, illumination and the like in which one or more fiberoptic waveguides receive light from one or more diode lasers or diode laser bars and transmit the light to an output end where it is focused or collimated into a bright light image. The input end of the fiberoptic waveguide may be squashed into an elongated cross section so as to guide light emitted from an elongated light source such as a diode laser bar. The waveguides are preferably arranged at the output end into a tightly packed bundle where a lens or other optical means focuses or collimates the light. The bundle has a fused output end with a taper to a smaller output diameter, thereby producing a spatially uniform high power density light output. For diode laser bars much wider than 100 microns, a plurality of waveguides may be arranged in a line to receive the light, and then stacked at the output in a less elongated configuration. In this manner, light from many diode lasers or laser bars may be coupled through the bundle into the end of solid state laser medium.

Lamp-based laser simulator

Abstract: Conventional omnidirectional lamp light is converted into a narrowly focused, highly intense beam with a power comparable to certain types of lasers. The lamp light is collected and focused with conventional means into an optical coupling cone which condenses the conventionally-focused beam to a very small diameter for launching into a fiber optic cable. An optical terminator at the end of the optical fiber retains collimation of the beam and a power density comparable to certain types of lasers, such as those used in medical applications.

Imaging process and system for transillumination with photon frequency marking

Abstract: In an imaging process and system by transillumination of a medium (H) illuminated by transparency by a beam (F1), an acoustic transducer (TA1) emits an acoustic wave in the medium (H) which interferes with the beam (F1). The frequency of the light passing through the medium (H) is then shifted from the value of the frequency of the acoustic wave. A collimating device (A) whose object focus is located at the intersection of the acoustic wave and the light beam (F1) collects the light diffused by the medium (H). Application: medical imaging.

Method and apparatus for optically measuring characteristics of a thin film by directing a P-polarized beam through an integrating sphere at the brewster's angle of the film

Abstract: A method for optically measuring at least one characteristic of a thin film on a reflecting substrate. A p-polarized beam of collimated light of known intensity is directed through an integrating sphere onto the film at substantially the Brewster's angle of the film. All the light is reflected into the sphere, including all diffusely reflected light as well as the light specularly reflected at a region inside the sphere where the specularly reflected light is incident. A reflective surface is provided for determining the thickness of the film as a function of the total intensity of light sensed within the sphere. An absorptive surface is provided at said region for absorbing the specularly reflected light for determining the porosity or surface roughness of the film based on the intensity of the diffused light sensed within the sphere not reflected from the substrate.

X-ray diffraction inspection system

Abstract: An inspection system for detecting the presence of selected crystalline materials, such as explosives or drugs, utilizing an x-ray source and a collimated array of detectors to sense radiation scattered by the objects being inspected. A signal processing system compares the measured signal with selected spectra to determine whether specific materials are present within the inspected object.

Identification of RNO 43 and B335 as two highly collimated bipolar flows oriented nearly in the plane of the sky

Abstract: An analysis of CO and CS line observations shows that RNO 43 and B335 are single highly collimated bipolar flows oriented nearly in the plane of the sky. The angle between the line of sight and the flow axis is estimated to be 85 deg in RNO 43 and 82 deg in B335. The results indicate that each of these flows must have a significant expansion velocity perpendicular to its axis, and that the flow in B335 must be driven by a mostly nonmolecular wind component.

Chip mounting techniques for display apparatus

Abstract: Driver circuit chip mounting techniques for use in the fabrication of monolithic flat panel displays are disclosed in accordance with the teachings of the present invention. According to a preferred embodiment, a driver circuit having a spot of optical cement is precisely positioned within a location of metalized, grouped and patterned row or column conductors. Thereafter collimated ultraviolet light is imaged through the display onto the rear of the driver circuit until the optical cement has become sufficiently tacky to permit the display to be inverted whereupon collimated ultraviolet light may be directly applied to complete the full curing of the optical cements.

Densitometer for measuring specular reflectivity

Abstract: An infrared densitometer which measures the reduction in the specular component of reflectivity as marking particles are progressively deposited on a moving photoconductive belt. Collimated light rays are projected onto the marking particles. The light rays reflected from at least the marking particles are collected and directed onto a photodiode array. The photodiode array generates electricl signals proportional to the total flux and the diffuse component of the total flux of the reflected light rays. Circuitry compares the electrical signals and determines the difference therebetween to generate an electrical signal proportional to the specular component of the total flux of the reflected light rays.

Method and apparatus for measuring blood oxygen levels in selected areas of the eye fundus

Abstract: This invention provides for the measurement of relative oxygen saturation of the choriodal blood of the fundus of the eye of a subject by directing into the eye a source beam of light including incandescent, red and infrared light, the combined beam penetrating the choroid and impinging on the sclera of the eye, the beam then being reflected back out of the eye as a collimated beam of light. The collimated beam of light is directed to a dichroic beam splitter where the red and infrared light are separated from the beam and are subject to the measurement of their respective intensities. The measured intensities of the red and infrared light components of the collimated beam reflected from the eye are compared with the measured intensities of the red and infrared light components of the separated portion of the source beam of light to determine the ratio of oxyhemoglobin to reduced hemoglobin.

Clear holographic helmet visor and process of producing same

Abstract: The visor can be readily mounted on a helmet by virtue of the fact that it dispenses with the need for any optical relay system Provision is made for a light image generator, an optical combining and collimating assembly in which a holographic flat plate and a holographic spherical plate are grouped together so as to provide a view of the collimated image superimposed on the landscape The holographic spherical plate is employed off the axis and produces collimation in a pupil zone placed substantially at the focal distance of the apex of the spherical mirror The hologram of the spherical plate is recorded by means of a digital hologram in order to minimize aberrations The flat plate can be fairly steeply inclined with respect to the sighting axis and so designed as to reduce the ratio of parasitic reflection of the imaging channel

Three dimensional color display and system

Abstract: The disclosure relates to a three dimensional color display wherein controlled modulated laser light (3,7,11) of predetermined different frequencies (1,5,9) is transmitted via fiber optics (13,15,17) and combined in a fiber optic coupler (19) to provide a combined light beam. This light beam is transmitted along a fiber optic path (21) wherefrom it is collimated and a three dimensional color display is formed therefrom. The three dimensional display is provided by an x-y scanner (25) for forming a two dimensional image (27) from the light on the single fiber optic path, a rotating display screen (29) for causing each point on the two dimensional image to move along a path making an acute angle with the two dimensional image wherein operation of one of the scanner and the rotating display screen is controlled relative to the other.

Atomic beam collimation using a laser diode with a self-locking power-buildup cavity

Abstract: We have demonstrated a self-locking power-buildup cavity for laser diodes. This device requires only a few simple optical elements and can provide a standing wave containing as much as 1000 times the power emitted by the laser diode. With this device we have obtained an intense standing wave of tunable light that was used to collimate a cesium atomic beam. We have studied the power and frequency dependence of the beam collimation.

Optical performance of the Naval Research Laboratory's Materials Analysis Beam Line at the NSLS

Abstract: The optical performance of the Naval Research Laboratory's Materials Analysis Beam Line at the National Synchrotron Light Source is reported. Photon fluxes into the experimental hutch were measured over the energy range from 3 to 11 keV. Two sets of flux data were taken, one with no slits in the beam and the other with a 2.5 mm diameter slit which passed only the best focused portion of the beam. At 6 keV, a total flux in excess of 2 × 109 photons/(s mA) of stored current was observed. The focal spot was mapped at several energies using a pinhole and a detector which were mounted on a two dimensional translation stage. At 6 keV the fwhm dimensions of the focal spot were 1.0 mm horizontally, and 3.0 mm vertically. The energy spread in the monochromatic beam was estimated by measuring the width of a narrow pre-edge feature of manganese in KMnO4 at 6.5 keV. The spread was minimized by adjusting the curvature and incident angle of a collimating mirror upstream of the beam line's monochromator. At 6.5 keV an energy spread of 2.6 eV was observed. These measured quantities of flux, spot size and energy resolution are compared to their expected values [1,2] to give an overall view of the performance of the optics.

Measurement of the coherence length of highly collimated X‐rays from the visibility of equal‐thickness fringes

Abstract: The coherence length of highly collimated X-rays produced by a collimator system, using successive asymmetric reflections, has been determined for the first time from the visibility of equal-thickness fringes in the Laue geometry. Observed transverse and longitudinal components of the coherent length were more than 220 and 40 μm, respectively, at a wavelength of 0.70 A.

The 6 m Point-Focusing Small-Angle X-ray Scattering Camera at the High-Intensity X-ray Laboratory of Kyoto University

Abstract: A new multipurpose X-ray small-angle scattering camera system consisting of a rotating-anode X-ray generator, a double-focusing collimator and a two-dimensional position-sensitive detector has been developed at the High-Intensity X-ray Laboratory of Kyoto University. The overall camera length is 6 m, and the sample-to-detector distance can be varied in 0.5 m increments up to 3 m to cover scattering angles ranging from 0.001 to 0.18 rad. The collimator consists of a pair of crossed-plane total-reflection mirrors of 40 cm in length. The mirrors, which are mechanically bent to form cylindrical surfaces, provide point collimation free of collimation error. General-purpose sample holders equipped with a programmable temperature controller are provided for both transmission and scattering measurements; the temperature is maintained within ± 0.1 K in the range of 223–573 K. A cryostat for measurements down to 20 K, a dynamic sample deformation apparatus, and a temperature-jump equipment are also available. The multi-wire delay-line position-sensitive proportional counter has an active area of 128 × 128 mm with a spatial resolution of 0.5 × 1.0 mm. The data acquisition is controlled by a real-time front-end processor through a CAMAC interface. The data are recorded in a dual-port histogramming memory of 32 bit × 1 Mwords, which enables direct access to the data from the main computer for real-time monitoring and analysis. The performance of the camera is demonstrated with some selected examples: diffraction patterns from carp lateral line nerve myelin and chicken-tendon collagen fibrils, a Guinier plot of the scattering from polystyrene in dilute solution, and time-resolved measurements of polypropylene during the annealing process.

Method and device for the determination of the spatial coordinates of any arbitrary measuring point

Abstract: The method for the determination of the spatial coordinates of any arbitrary measuring point (X) with the aid of an electronic theodolite (1) having an electronic distance measuring device (2) uses a collimated laser beam (4), which is projected into the central axis (N) of the distance measuring device. This laser beam (4) designates the target point or measuring point (Z or X), at which a reflector (3) for the distance measurement can be set. The measured distance, together with the horizontal circle values and vertical circle values determined by the theodolite (1), is digitised, converted into coordinates and further processed by a computer (5) operationally coupled to the said devices.

Method and apparatus for generating a straight reference line

Abstract: A system for generating a spatially stable, small diameter light beam (18) which serves as a straight reference line over long distances may use the direction of propagation of light and one fixed point (11, 12) or may be between two fixed points (12, 21). In either instance, a light source (1) emits a beam (2) which is expanded, collimated and spatially filtered (3, 4). In the first instance, the collimated light wave (11) produced is diffracted by a sphere (12) to produce the small diameter light beam (18) which is constituted by a continuum of spots (16) which, in turn, produces a Poisson's spot (16) on a detector (21) which spatially samples the intensity of the spot (16). The resultant voltage (22) from each active detection are sent to a center locating electronics/computer (24) which processes the voltages (22) to give the position of the detector (21) relative to the straight reference line (18). In the second instance, the collimated light wave (11) is produced by reflecting the beam (5) passing through the pinhole (4) from a steering mirror (6) which can be tilted about two axes by applying error signal voltages (27, 28) to tilt adjusters (7, 8) which are related to the displacement of spot (16) from the center of detector (21) in the X and Y directions. The tilting of the mirror (6) changes the angle of incidence of the light wave (11) on the sphere (12) so that the spot (16) is centered on the detector (21).

Embedded fiber optic beam displacement sensor

Abstract: A method and apparatus for the two dimensional measurement of displacements of sample materials using a photodetector grid array and optical fiber embedded in the test specimen The system consists of a light source which is passed into one end of an optical fiber which has been embedded a beam specimen, so that when the beam is placed in motion, the light traverses through the fiber and emerges from the opposite end where its projected image traces a pattern simulating that of the beam In a preferred embodiment, the collimated exiting light is incident upon a light beam splitter which directs equal portions of the light toward a quadrant photovoltaic cell device and toward a charge couple device (CCD) The CCD is connected to an optoelectronic viewing device for initial calibration, display and monitoring The photodetector array is connected to a translator/amplifier which increases the photocells' source currents and converts them to equivalent voltages for output to a digital data processing terminal The processing terminal integrates all simultaneous measurements by vectorial resolution of the voltage related deflections' magnitude and direction

Thermoacoustic generation of narrow‐band signals with high repetition rate pulsed lasers

Abstract: The generation of sound by absorption of laser light in water is analyzed for the case of lasers pulsating at high repetition rates. It is shown that pulsating the laser at any arbitrary repetition rate is, in general, not a very effective way to produce a narrow‐band signal. In order to produce a signal with a narrow frequency band, one should instead pulsate the laser at an optimum repetition rate that is determined by the optical frequency of the laser and, to a lesser extent, by the laser beam diameter. Expressions for the optimum repetition rate are derived from both a frequency domain analysis and a time domain analysis. It is found that, with the present laser technology, significant gain in signal‐to‐noise ratio can be achieved by pulsating the laser at its optimum repetition rate, as compared with the more conventional methods for generation of narrow‐band signals, such as the method of laser intensity modulation. As a result, it now seems possible to generate continuous thermoacoustic highly collimated sound beams with high repetition pulsed lasers in such a way that these signals are easily detectable several kilometers away from the source. Spatially periodic laser deposition configurations on the water surface are also discussed, and it is shown that further improvement in signal‐to‐noise ratio is achievable, in principle, for a spatial periodicity tuned to the optimum temporal periodicity of the repetition rate of the pulsed laser.

Beam scanner with distortion correction

Abstract: An optical apparatus for an image forming apparatus has a laser emission device. The laser emission device has first and second light emission units for emitting first and second laser beams. The first and second laser beams emitted by the light emission units are collimated by a collimator lens, and their radii are regulated by a stop. These laser beams are scanned by a scanning mirror on a photosensitive drum in the main scan direction. Distortion of the scanned first and second laser beams is corrected by first and second f-θ lenses. In these f-θ lenses, power for focusing the laser beams in the sub-scan direction is larger than power for focusing the laser beam in the main scan direction.

Correction for scattered radiation and other background signals in dual-energy computed tomography material thickness measurements

Abstract: Both beam hardening and the detection of scattered radiation cause nonlinearity errors in x-ray computed tomography (CT), leading to artifacts and CT number inaccuracies. Dual-energy measurements can be used to correct beam hardening effects to a high degree of accuracy. However, in the imaging of thick body sections the transmitted intensity of the primary beam is low, making scatter the most significant cause of CT number inaccuracy. Furthermore, the scatter-to-primary ratio is energy dependent, causing a shift in the apparent effective atomic number of the absorbing material. We have measured scatter under a variety of conditions on a third generation CT scanner with dual-energy capability in order to determine its effect on the accuracy of quantitative measurements. The effects of off focus radiation, detector cross-talk, and detector dark current were also accounted for in the analysis of the measured scatter data. Our results indicate that on this well collimated system, an accurate correction for scatter can be made based on the detected intensity in projections.

UV scanning system for centrifuge

Abstract: A centrifuge sample is optically scanned during centrifuging. The sample, placed in a centrifuge rotor having a cell with top and bottom windows, is spun until stratification and discrete layering occurs within the sample. Such layering oc­ curs on layers that are precisely normal to the radius of the centrifuge at the point of sample and parallel to the spin axis of the centrifuge. A slit scanner having a slit normal to the sample plane transverses the width of the sample below the cell to detect with precision the precise location of the strata in the cell. A light source is reflected by a toroidal mirror having two radius of curvature. One radius of curvature is selected to collimate rays of light parallel to the layer of the sample. The mirror is ruled with respect to the other radius of curvature to chromatically classify light to preselect band width. Rotation of the mirror preserved collimation but enables selected scanning light frequency.

Diode pumped modelocked solid state laser

Abstract: In a three-mirror optical resonator, solid state laser, the gain member is a thin slab, such as Nd:glass, disposed at Brewsters angle to minimize insertion loss. The gain slab is disposed at a beam waist in a confocal arm of the optical resonator. Optical pumping radiation from a laser diode source is focused through one of the concave mirrors of the confocal arm of the resonator into the gain slab. The second arm of the resonator is defined between a planar mirror and one of the confocal mirrors. An acousto-optic mode-locking modulator is disposed in the collimated beam region of the resonator proximate the planar mirror. Additional pumping diodes pump collinearly through the other confocal mirror for higher power operation. The slab is rotated and translated to average thermally induced stress and de-focusing effects.

Coupling device for high power laser beam transmitting optical fibers

Abstract: A fiber optic coupling device for coupling two optical fibers transmitting a high power laser beam is disclosed. In one embodiment, the device comprises a first lens to collimate the beam delivered by one of the optical fibers and a second lens to focus that collimated beam onto the end of the other fiber for injection therein and continued transmission of the power laser beam through the second fiber.

Recursive design for an efficient HOE with different recording and readout wavelengths.

Abstract: The design of a holographic optical element for focusing a collimated off-axis beam to an on-axis point is described. It is designed according to a novel recursive technique in which the recording is done at a wavelength which differs from the readout. In this recursive technique the final holographic optical element is recorded by using other holograms to provide the aspheric recording wavefronts necessary for reducing the aberrations and maximizing the diffraction efficiency. The design is illustrated with an example where an f/3.0 focusing element is recorded at 514.5 nm and read out at 1064 nm. A spot size of 15microm and a diffraction efficiency of ~60% were measured.