Showing papers on "Collimated light published in 2009"

System and method for measuring irregular objects with a single camera

Abstract: An optical system for measuring an irregularly shaped object includes a dimensioning station having a base, a first wall extending from the base, and a second wall extending from the base. A collimated light is passed from each of first and second collimated light sources arranged generally parallel to the base, illuminating the first and second walls and defining first and second shadows, respectively. A camera is arranged to obtain image data representing each of the first and second shadows. The system is configured to collect the image data for determining at least one dimension of an object from each of the first and second shadows. Each of the first and second collimated light sources may be a light with a collimating lens arranged between the light and the respective wall. The light source may be an LED and the collimating lens may be a collimating Fresnel lens.

Ultra‐small‐angle X‐ray scattering at the Advanced Photon Source

Abstract: The design and operation of a versatile ultra-small-angle X-ray scattering (USAXS) instrument at the Advanced Photon Source (APS) at Argonne National Laboratory are presented. The instrument is optimized for the high brilliance and low emittance of an APS undulator source. It has angular and energy resolutions of the order of 10−4, accurate and repeatable X-ray energy tunability over its operational energy range from 8 to 18 keV, and a dynamic intensity range of 108 to 109, depending on the configuration. It further offers quantitative primary calibration of X-ray scattering cross sections, a scattering vector range from 0.0001 to 1 A−1, and stability and reliability over extended running periods. Its operational configurations include one-dimensional collimated (slit-smeared) USAXS, two-dimensional collimated USAXS and USAXS imaging. A robust data reduction and data analysis package, which was developed in parallel with the instrument, is available and supported at the APS.

Measurement of bone mineral in vivo: an improved method

Abstract: The mineral content of bone can be determined by measuring the absorption by bone of a monochromatic, low-energy photon beam which originates in a radioactive source (iodine-125 at 27.3 kev or americium-241 at 59.6 kev). The intensity of the beam transmitted by the bone is measured by counting with a scintillation detector. Since the photon source and detector are well collimated, errors resulting from scattered radiation are reduced. From measurements of the intensity of the transmitted beam, made at intervals across the bone, the total mineral content of the bone can be determined. The results are accurate and reproducible to within about 3 percent.

Enhanced collimated GeV monoenergetic ion acceleration from a shaped foil target irradiated by a circularly polarized laser pulse.

Abstract: Using multidimensional particle-in-cell simulations we study ion acceleration from a foil irradiated by a circularly polarized laser pulse at 10;{22} W/cm;{2} intensity. When the foil is shaped initially in the transverse direction to match the laser intensity profile, three different regions (acceleration, transparency, and deformation region) are observed. In the acceleration region, the foil can be uniformly accelerated for a longer time compared to a usual flat target. Undesirable plasma heating is effectively suppressed. The final energy spectrum of the accelerated ion beam in the acceleration region is improved dramatically. Collimated GeV quasi-monoenergetic ion beams carrying as much as 19% of the laser energy are observed in multidimensional simulations.

Flat panel lens

Abstract: A flat panel lens system as a tapered light guide that has minimal or no margin for fan out. The tapered light guide includes a thin end, and a thick end of which is a bevelled mirror or an optical equivalent. Light is injected into the thin end and the mirror is such that rays injected through a point at the thin end emerge collimated from one of the light guide surfaces, and that collimated rays injected at an appropriate angle through one of the light guide surfaces emerge from a point at the thin end. Bragg gratings can be utilized for color implementations as well. The tapered light guide can be fabricated as a single piece, by extrusion, injection molding, or the combination/variation of extrusion and injection molding, as well as other commonly known techniques.

Thin illumination system

Abstract: The present invention introduces a new class of thin doubly collimating light distributing engines for use in a variety of general lighting applications. Output illumination from these slim-profile illumination systems whether square, rectangular or circular in physical aperture shape is directional, square, rectangular or circular in beam cross-section, and spatially uniform and sharply cutoff outside the system's adjustable far-field angular cone. Some embodiments provided include thin light distributing engines which provide input light collimated in one meridian and a light distributing element that maintains input collimation while collimating output light in the un-collimated orthogonal meridian, in such a manner that the system's far-field output light is collimated in both its orthogonal output meridians. The present invention can also include optical films that process the engine's doubly collimated output illumination so as to increase its angular extent one or both output meridians without changing beam shape or uniformity.

Collimated light from a waveguide for a display backlight.

Abstract: We report light collimation from a point source without the space normally needed for fan-out. Rays emerge uniformly from all parts of the surface of a blunt wedge light-guide when a point source of light is placed at the thin end and the source’s position determines ray direction in the manner of a lens. A lenticular array between this light-guide and a liquid crystal panel guides light from color light-emitting diodes to designated sub-pixels thereby removing the need for color filters and halving power consumption but we foresee much greater power economies and wider application.

Coherent and collimated blue light generated by four-wave mixing in Rb vapour

Abstract: We investigate frequency up-conversion of low power cw resonant radiation in Rb vapour as a function of various experimental parameters. We present evidence that the process of four wave mixing is responsible for unidirectional blue light generation and that the phase matching conditions along a light-induced waveguide determine the direction and divergence of the blue light. Velocity-selective excitation to the 5D level via step-wise and two-photon processes results in a Doppler-free dependence on the frequency detuning of the applied laser fields from the respective dipole-allowed transitions. Possible schemes for ultraviolet generation are discussed.

New technology enables high precision multislit collimators for microbeam radiation therapy.

Abstract: During the past decade microbeam radiation therapy has evolved from preclinical studies to a stage in which clinical trials can be planned, using spatially fractionated, highly collimated and high intensity beams like those generated at the x-ray ID17 beamline of the European Synchrotron Radiation Facility. The production of such microbeams typically between 25 and 100 microm full width at half maximum (FWHM) values and 100-400 microm center-to-center (c-t-c) spacings requires a multislit collimator either with fixed or adjustable microbeam width. The mechanical regularity of such devices is the most important property required to produce an array of identical microbeams. That ensures treatment reproducibility and reliable use of Monte Carlo-based treatment planning systems. New high precision wire cutting techniques allow the fabrication of these collimators made of tungsten carbide. We present a variable slit width collimator as well as a single slit device with a fixed setting of 50 microm FWHM and 400 microm c-t-c, both able to cover irradiation fields of 50 mm width, deemed to meet clinical requirements. Important improvements have reduced the standard deviation of 5.5 microm to less than 1 microm for a nominal FWHM value of 25 microm. The specifications of both devices, the methods used to measure these characteristics, and the results are presented.

A three-dimensional multispectral fluorescence optical tomography imaging system for small animals based on a conical mirror design

Abstract: We have developed a three dimensional (3D) multispectral fluorescence optical tomography small animal imaging system with an innovative geometry using a truncated conical mirror, allowing simultaneous viewing of the entire surface of the animal by an EMCCD camera. A conical mirror collects photons approximately three times more efficiently than a flat mirror. An x-y mirror scanning system makes it possible to scan a collimated excitation laser beam to any location on the mouse surface. A pattern of structured light incident on the small animal surface is used to extract the surface geometry for reconstruction. A finite element based algorithm is applied to model photon propagation in the turbid media and a preconditioned conjugate gradient (PCG) method is used to solve the large linear system matrix. The reconstruction algorithm and the system feasibility are evaluated by phantom experiments. These experiments show that multispectral measurements improve the spatial resolution of reconstructed images. Finally, an in vivo imaging study of a xenograft tumor in a mouse shows good correlation of the reconstructed image with the location of the fluorescence probe as determined by subsequent optical imaging of cryosections of the mouse.

Collimated blue light generated by four-wave mixing in Rb vapour

Abstract: We investigate frequency up-conversion of low power cw resonant radiation in Rb vapour as a function of various experimental parameters. We present evidence that the process of four wave mixing is responsible for unidirectional blue light generation and that the phase matching conditions along a light-induced waveguide determine the direction and divergence of the blue light. Velocity-selective excitation to the 5D level via step-wise and two-photon processes results in a Doppler-free dependence on the frequency detuning of the applied laser fields from the respective dipole-allowed transitions. Possible schemes for ultraviolet generation are discussed.

Design of optimal collimation for dedicated molecular breast imaging systems

Abstract: Molecular breast imaging (MBI) is a functional imaging technique that uses specialized small field-of-view gamma cameras to detect the preferential uptake of a radiotracer in breast lesions. MBI has potential to be a useful adjunct method to screening mammography for the detection of occult breast cancer. However, a current limitation of MBI is the high radiation dose (a factor of 7-10 times that of screening mammography) associated with current technology. The purpose of this study was to optimize the gamma camera collimation with the aim of improving sensitivity while retaining adequate resolution for the detection of sub-10-mm lesions. Square-hole collimators with holes matched to the pixilated cadmium zinc telluride detector elements of the MBI system were designed. Data from MBI patient studies and parameters of existing dual-head MBI systems were used to guide the range of desired collimator resolutions, source-to-collimator distances, pixel sizes, and collimator materials that were examined. General equations describing collimator performance for a conventional gamma camera were used in the design process along with several important adjustments to account for the specialized imaging geometry of the MBI system. Both theoretical calculations and a Monte Carlo model were used to measure the geometric efficiency (or sensitivity) and resolution of each designed collimator. Results showed that through optimal collimation, collimator sensitivity could be improved by factors of 1.5-3.2, while maintaining a collimator resolution of either < or =5 or < or = 7.5 mm at a distance of 3 cm from the collimator face. These gains in collimator sensitivity permit an inversely proportional drop in the required dose to perform

Image-guided small animal radiation research platform: calibration of treatment beam alignment

Abstract: Small animal research allows detailed study of biological processes, disease progression and response to therapy with the potential to provide a natural bridge to the clinical environment. The small animal radiation research platform (SARRP) is a portable system for precision irradiation with beam sizes down to approximately 0.5 mm and optimally planned radiation with on-board cone-beam CT (CBCT) guidance. This paper focuses on the geometric calibration of the system for high-precision irradiation. A novel technique for the calibration of the treatment beam is presented, which employs an x-ray camera whose precise positioning need not be known. Using the camera system we acquired a digitally reconstructed 3D 'star shot' for gantry calibration and then developed a technique to align each beam to a common isocenter with the robotic animal positioning stages. The calibration incorporates localization by cone-beam CT guidance. Uncorrected offsets of the beams with respect to the calibration origin ranged from 0.4 mm to 5.2 mm. With corrections, these alignment errors can be reduced to the sub-millimeter range. The calibration technique was used to deliver a stereotactic-like arc treatment to a phantom constructed with EBT Gafchromic films. All beams were shown to intersect at a common isocenter with a measured beam (FWHM) of approximately 1.07 mm using the 0.5 mm collimated beam. The desired positioning accuracy of the SARRP is 0.25 mm and the results indicate an accuracy of 0.2 mm. To fully realize the radiation localization capabilities of the SARRP, precise geometric calibration is required, as with any such system. The x-ray camera-based technique presented here provides a straightforward and semi-automatic method for system calibration.

Quasimonoenergetic electron beams with relativistic energies and ultrashort duration from laser-solid interactions at 0.5 kHz.

Abstract: We investigate the production of electron beams from the interaction of relativistically-intense laser pulses with a solid-density SiO2 target in a regime where the laser pulse energy is -mJ and the repetition rate -kHz. The electron beam spatial distribution and spectrum were investigated as a function of the plasma scale length, which was varied by deliberately introducing a moderate-intensity prepulse. At the optimum scale length of λ/2, the electrons are emitted in a collimated beam having a quasimonoenergetic distribution that peaked at -0.8MeV. A highly reproducible structure in the spatial distribution exhibits an evacuation of electrons along the laser specular direction and suggests that the electron beam duration is comparable to that of the laser pulse. Particle-in-cell simulations which are in good agreement with the experimental results offer insights on the acceleration mechanism by the laser field. © 2009 The American Physical Society.

Thermal interaction of short-pulsed laser focused beams with skin tissues.

Abstract: Time-dependent thermal interaction is developed in a skin tissue cylinder subjected to the irradiation of a train of short laser pulses. The skin embedded with a small tumor is stratified as three layers: epidermis, dermis and subcutaneous fat with different optical, thermal and physiological properties. The laser beam is focused to the tumor site by an objective lens for thermal therapy. The ultrafast radiation heat transfer of the focused beam is simulated by the transient discrete ordinates method. The transient Pennes bio-heat equation is solved numerically by the finite volume method with alternating direction implicit scheme. Emphasis is placed on the characterization of the focused beam propagation and absorption and the temperature rise in the focal spot. The effects of the focal spot size and location, the laser power, and the bio-heat equation are investigated. Comparisons with collimated irradiation are conducted. The focused beam can penetrate a greater depth and produce higher temperature rise at the target area, and thus reduce the possibility of thermal damage to the surrounding healthy tissue. It is ideal for killing cancerous cells and small tumors.

Directional light extraction enhancement from GaN-based film-transferred photonic crystal light-emitting diodes

Abstract: Experimental investigation of the directionality in the far-field pattern and light extraction enhancement in collected cone were performed in GaN-based film-transferred photonic crystal (PhC) light-emitting diodes (FTLEDs). Angular-resolved measurement revealed directional profile and azimuthal anisotropy in the far-field distribution with guided modes extraction. Good agreement according to Bragg’s diffraction theory and free photon band structure were achieved. The light enhancement in PhC FTLEDs compared to non-PhC FTLEDs within the collection cone angle was obtained according to measured three-dimensional far-field patterns. In a ±20° collection cone, collected light was enhanced by a factor of ∼2.4 for the collimated PhC FTLED.

Development of the fast astigmatic auto-focus microscope system

Abstract: In this paper, a fast auto-focus microscope system was developed based on the astigmatic method. A collimated infrared laser beam was employed in the infinite-corrected microscope optical axis by the beam splitter and reflected by the sample surface. By embedding an astigmatic lens in the system, the reflected laser beam has different focal lengths in the sagittal and tangential planes. As the microscope's relative distance varies, the reflected laser beam shape also varies and can be detected by an embedded four-quadrant photodiode, i.e., the focus error signal (FES) can be found. Then, a fast auto-focus system can be realized by converting the FES to the microscope's defocus distance. We designed an astigmatic auto-focus system for a 20× objective lens with a ±50 µm working range, and this system could also be used for 10× and 5× objectives with ±200 µm and ±800 µm working ranges, respectively.

Spatial and spectral properties of the high-order harmonic emission in argon for seeding applications

Abstract: We characterize and control the harmonic emission in the spectral and spatial domains in order to define in which conditions the harmonic radiation can be a high-quality seed for soft x-ray and x-ray free-electron lasers. The length of the gas cell, where harmonics are generated, was optimized and the energy per pulse was determined in absolute value with a calibrated x-ray photodiode. The beam spatial profile was measured and, in some conditions, a very collimated beam with a half-angle divergence below 1 mrad could be obtained. We also show that increasing the intensity of the fundamental laser field leads to a considerable broadening of the bandwidth of the harmonic radiation, allowing us to cover a large spectral range. This effect is due to fundamental reshaping leading to an efficient phase matching of both short- and long-trajectory contributions.

Dynamic manipulation of a laser beam using a liquid crystal spatial light modulator

Abstract: This article describes a graduate level optics laboratory experiment on the manipulation of the wavefront of a laser beam using a spatial light modulator. A computer generated holography technique is employed to generate a custom defined wavefront, realized in the +1 diffraction order when a collimated laser beam is diffracted by a binary transmission hologram. The hologram is written on a liquid crystal spatial light modulator and can be updated at a video rate using a personal computer interface.

Lighting device with adjustable light beam, particularly for a flashlight

Abstract: An adjustable light beam lighting device, particularly for a flashlight, has in succession along an axis a light source, a collimator collimating the light into a collimated beam, and a first optical element and a second optical element provided with respective arrays of side-by-side lenses arranged according to a network pattern. The lenses of the first element face respective lenses of the second element and are shaped to, respectively, converge and diverge the light from the collimated beam. A mask between the elements is shaped to laterally screen the light exiting from each lens of the first element and to convey the light exiting from each lens of the first element only on the facing lens of the second element, thus screening the adjacent lenses. A movement mechanism translates the elements with along the axis to vary the width of the beam emitted by the device.

Reduction of the secondary neutron dose in passively scattered proton radiotherapy, using an optimized pre-collimator/collimator

Abstract: Proton radiotherapy represents a potential major advance in cancer therapy. Most current proton beams are spread out to cover the tumor using passive scattering and collimation, resulting in an extra whole-body high-energy neutron dose, primarily from proton interactions with the final collimator. There is considerable uncertainty as to the carcinogenic potential of low doses of high-energy neutrons, and thus we investigate whether this neutron dose can be significantly reduced without major modifications to passively scattered proton beam lines. Our goal is to optimize the design features of a patient-specific collimator or pre-collimator/collimator assembly. There are a number of often contradictory design features, in terms of geometry and material, involved in an optimal design. For example, plastic or hybrid plastic/metal collimators have a number of advantages. We quantify these design issues, and investigate the practical balances that can be achieved to significantly reduce the neutron dose without major alterations to the beamline design or function. Given that the majority of proton therapy treatments, at least for the next few years, will use passive scattering techniques, reducing the associated neutron-related risks by simple modifications of the collimator assembly design is a desirable goal.

NGC7538 IRS1 - an ionized jet powered by accretion

Abstract: Analysis of high spatial resolution VLA images shows that the free-free emission from NGC7538 IRS1 is dominated by a collimated ionized wind. We have re-analyzed high angular resolution VLA archive data from 6 cm to 7 mm, and measured separately the flux density from the compact bipolar core and the extended (1.5" - 3") lobes. We find that the flux density of the core is proportional to the frequency to the power of alpha, with alpha being about 0.7. The frequency dependence of the total flux density is slightly steeper with alpha = 0.8. A massive optically thick hypercompact core with a steep density gradient can explain this frequency dependence, but it cannot explain the extremely broad recombination line velocities observed in this source. Neither can it explain why the core is bipolar rather than spherical, nor the observed decrease of 4% in the flux density in less than 10 years. An ionized wind modulated by accretion is expected to vary, because the accretion flow from the surrounding cloud will vary over time. BIMA and CARMA continuum observations at 3 mm show that the free-free emission still dominates at 3 mm. HCO+ J = 1 - 0 observations combined with FCRAO single dish data show a clear inverse P Cygni profile towards IRS1. These observations confirm that IRS1 is heavily accreting with an accretion rate of about 2 times 10(-4) solar masses per year.

High energy X-ray transfocator based on Al parabolic refractive lenses for focusing and collimation

Abstract: We describe an X-ray transfocator – a lens assembly whose focal length can be continuously adjusted by the mechanical movement of one or more groups of individual lenses. The transfocator consists of 7 cylindrical cartridges containing 2, 4, 8, 16, 32, 64 and 128 Al parabolic lenses respectively. Pneumatic actuators are used to bring cartridges in and out of the beam independently providing collimation or focusing at a desired distance downstream. The transfocator is installed in the ID11 extension beamline at 90 m from the source. The tests were performed at the energy range between 25 and 60 keV X-ray energy.

Coherent 455nm beam production in cesium vapor

Abstract: We observe coherent, continuous wave, 455nm blue beam production via frequency up-conversion in cesium vapor. Two infrared lasers induce strong double-excitation in a heated cesium vapor cell, allowing the atoms to undergo a double cascade and produce a coherent, collimated, blue beam co-propagating with the two infrared pump lasers.

GRB 060605: multi-wavelength analysis of the first GRB observed using integral field spectroscopy

Abstract: The long and relatively faint gamma-ray burst GRB 060605 detected by Swift/BAT lasted about 20 sec. Its afterglow could be observed with Swift/XRT for nearly 1 day, while Swift/UVOT could detect the afterglow during the first 6 hours after the event. Here, we report on integral field spectroscopy of its afterglow performed with PMAS /PPak mounted at the Calar Alto 3.5 m telescope. In addition, we report on a detailed analysis of XRT and UVOT data and on the results of deep late-time VLT observations that reveal the GRB host galaxy. We find t hat the burst occurred at a redshift of z=3.773, possibly associated with a faint, RC = 26.4± 0.3 host. Based on the optical and X-ray data, we deduce information on the SED of the afterglow, the position of the cooling frequency in the SED, the nature of the circumburst environment, its collimation factor, and its energetics. We find that the GRB fi reball was expanding into a constant-density medium and that the explosion was collimated with a narrow half-opening angle of about 2.4 degrees. The initial Lorentz factor of the fireball was about 250; however, its beaming-corrected energy release in the gamma-ray band was comparably low. The optical, X-ray afterglow, on the other hand, was rather luminous. Finally, we find that the data are consistent withi n the error bars with an achromatic evolution of the afterglo w during the suspected jet break time at about 0.27 days after the burst.

Method and apparatus for controlling the size of a laser beam focal spot

Abstract: A method and apparatus is described that allows the width of fine line structures ablated or cured by a focussed laser beam on the surface of flat substrates to be dynamically changed while the beam is in motion over the substrate surface while simultaneously maintaining the beam focal point accurately on the surface. A three-component variable optical telescope is used to independently control the beam diameter and collimation by movement of first and second optical components relative to the third optical component. The method allows different focal spot diameters and different ablated or cured line widths to be rapidly selected and ensures that the beam shape in the focal spot remains constant and the depth of focus is always maximized.

Analytic modal solution to transmission and collimation of light by one- dimensional nanostructured subwavelength metallic slits

Abstract: Light transmitting through a subwavelength slit on an ordinary metal plate is diffracted to all directions but if the exit plane of the slit is patterned with periodical nanostructures, the diffracted light may be compressed into a collimated beam within a small angle. In this paper, we develop a rigorous theoretical method for solving the surface wave induced beam collimation in nanostructured subwavelength metallic slits. The method combines the analytical modal expansion method, the supercell technique, the transfer-matrix method, and the conventional Kirchhoff’s diffraction theory. It allows for quantitative investigation of coupling of the incident light into the guided wave of the slit and coupling of the guided wave out of the nanostructured exit plane. We have used the method to examine light transmission through the nanostructured metallic slit and the corresponding diffraction and beam collimation behaviors. We have extensively analyzed the angular transmission spectrum as a function of the nano...

Luminaire and method of operation

Abstract: A luminaire and a method of operating a luminaire is provided. The luminaire includes a light source emitting a plurality of light rays. A collimation device is arranged to receive a portion of light from the light source and transmits the portion of light through an exit aperture towards an illuminated area. The exit aperture includes a planar portion and at least one lenslet formed thereon. The lenslet is arranged having a first profile and a second profile, where the portion of light is refracted on a plurality of angles to form a twisted profile by the lenslet.

Light recycling directional control element and light emitting device using the same

Abstract: In one embodiment of this invention, an optical element comprises a light recycling directional control element and provides increased spatial color or luminance uniformity, desired angular color uniformity, and customizable light re-direction properties. In one embodiment, the optical element comprises at least one light blocking region and a lenticular lens element. Further embodiments incorporate an anisotropic light backscattering region within a light transmitting layer. The optical element may further comprise a light collimating element or an additional light lenticular lens element and light transmitting region that may be oriented parallel or perpendicular to the first lenticular lens element. Light emitting devices and displays incorporating the light recycling direction control element are further embodiments of this invention.