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Showing papers on "Collimated light published in 1999"


Journal ArticleDOI
TL;DR: In this article, self-determining collimated light is generated in a photonic crystal fabricated on silicon and the divergence of the collimated beam is insensitive to that of the incident beam and much smaller than the divergence generated in conventional Gaussian optics.
Abstract: We found that self-determining collimated light is generated in a photonic crystal fabricated on silicon. The divergence of the collimated beam is insensitive to that of the incident beam and much smaller than the divergence that would be generated in conventional Gaussian optics. The incident-angle dependence of the self-collimated light propagation including lens-like divergent propagation was interpreted in terms of the highly modulated dispersion surfaces with inflection points, where the curvature changes from downward to upward corresponding to respectively a concave/convex-lens case. This demonstration is an important step towards controlling beam profile in photonic crystal integrated light circuits and towards developing “photonic crystalline optics.”

717 citations


Journal ArticleDOI
TL;DR: The BEAM Monte Carlo code is used to simulate the 60Co beam from an Eldorado 6 radiotherapy unit and to calculate the relative air-kerma output factors as a function of field size, and the results accurately predict the effects of electron contamination from the surface to dose maximum.
Abstract: The BEAM Monte Carlo code is used to simulate the 60Co beam from an Eldorado 6 radiotherapy unit and to calculate the relative air-kerma output factors as a function of field size. The unit is realistically modeled, including source capsule, housing and collimator assembly. The calculated relative air-kerma output factors at SSD=80.5 cm agree to within 0.1% with measured values. It is shown that the variation of the output factor is almost entirely due to scattered photons from the fixed and adjustable collimators and there is no effect of shadowing primary photons. The influence of the geometry of the collimation system on the photon spectra on-axis is shown to be small but finite. The calculated buildup region of a depth-dose curve in a water phantom irradiated by a narrow and a broad 60Co beam is shown to agree with experimental data at the 2% to 3% level. Unlike previous calculations, the results accurately predict the effects of electron contamination from the surface to dose maximum. The variation of electron contamination with field size is also presented, as are spectra as a function of field size.

177 citations


Patent
08 Oct 1999
TL;DR: A fingerprint optical input apparatus comprises a contact image sensor for viewing a moving finger and providing a high contrast image as discussed by the authors, where a narrow strip of the fingerprint touching a transparent platen is illuminated by sheet of collimated light normal to or at an oblique angle to the surface.
Abstract: A fingerprint optical input apparatus comprises a contact image sensor for viewing a moving finger and providing a high contrast image. A narrow strip of the fingerprint touching a transparent platen is illuminated by sheet of collimated light normal to or at an oblique angle to the surface. The fingerprint image is viewed at an oblique angle by partially scattered light or by frustrated total internal reflection by a GRIN rod lens array and projected onto a linear array sensor. Various embodiments of the platen provide a compact design by using TIR or mirror reflections of the fingerprint image.

174 citations


Patent
15 Dec 1999
TL;DR: In this paper, a light generator consisting of a light source in the form of a plurality of LEDs (3, 3′,... ), each having a luminous flux of at least 5 lm during operation, is presented.
Abstract: The light generator comprises a housing (1) with a light source in the form of a plurality of LEDs (3, 3′, . . . ), each having a luminous flux of at least 5 lm during operation. The housing (1) also comprises a collimating lens (6) and a Fresnel lens (8) for focusing the beam generated by the LEDs (3, 3′, . . . ). The light engine is further provided with drive means in a box (10) for driving the LEDs (3, 3′, . . . ). Preferably, the collimator lens (6) has a number of sub-lenses (7, 7′, . . . ), the optical axis of each of the sub-lenses coinciding with the optical axis of a respective one of the LEDs (3, 3′, . . .).

152 citations


Patent
20 Apr 1999
TL;DR: In this article, a long-focal-length lens was used to focus on the cornea through a small angle, as opposed to focusing a collimated light onto the retina, eliminating the need for lenses or lens combinations and the time required to adjust such to accommodate the different visual characteristics of each patient.
Abstract: Optical characteristics, including vision defects, of optical systems, such as the eye, are measured using a collimated beam from a diode laser focused at a position relative to the eye other than the retina for providing a finite source of secondary radiation on the retina of the eye, the image of which is close to a desired diffraction-limited spot. The secondary radiation is reflected back from the retina as a reflected wavefront of radiation that passes through the eye and is directed onto a wavefront analyzer where distortions associated with the reflected wavefront are measured. By focusing on the cornea through a long-focal-length lens and thus converging the beam through a small angle, as opposed to focusing a collimated light onto the retina, the need for lenses or lens combinations and the time required to adjust such to accommodate the different visual characteristics of each patient is eliminated.

147 citations


Patent
21 Jan 1999
TL;DR: In this paper, a magneto-optical head using a catadioptric focusing device comprised of an incident surface, bottom reflective surface, a pedestal, and a body is described.
Abstract: A magneto-optical head using a catadioptric focusing device comprised of an incident surface, a bottom reflective surface, a pedestal, and a body. The incident surface is generally flat and is comprised of a central diffractive, optically transmissive facet and a peripheral facet comprised of a kinoform phase profile. In a data writing or reading mode, an incident optical beam, such as a laser beam impinges upon the central facet, and is diffracted thereby. The incident laser beam can be collimated, convergent or divergent. The laser beam passes through the transparent body, and impinges upon the bottom reflective surface. The laser beam is then reflected by the bottom reflective surface, through the body, unto the kinoform phase profile. The laser beam is reflected and refracted by the peripheral kinoform phase profile as a focused beam, through the body, and is focused as a focal point. The focal point is preferably located at, or in close proximity to a pedestal edge, along a central axis, in very close proximity to the disk. This will allow the focused optical beam to propagate toward, or penetrate the disk through evanescent wave coupling, for enabling the transduction of data to and from the disk.

135 citations


Patent
29 Oct 1999
TL;DR: In this article, a light guide with a collimating unit provided at least on one side of the light guide for collimating rays incident on the guide, and a light source disposed in the vicinity of the collimating units and surrounded by a reflector is presented.
Abstract: An illumination apparatus provides an improved light utilization efficiency and improved collimation. The illumination apparatus has a light guide, a collimating unit provided at least on one side of the light guide for collimating rays incident on the light guide, and a light source disposed in the vicinity of the collimating unit and surrounded by a reflector. Preferably, in order for the light guide to be able to emit collimated light uniformly from its emission surface, the light guide has inclined reflecting irregularities or stepwise reflecting plates which are provided directly or via an air gap on a back surface opposite to the emission surface thereof, wherein the inclined reflecting plates are specular-finished at least on the inclined portions.

105 citations


Patent
14 Jan 1999
TL;DR: In this paper, a network for multi-bit word parallel communication between optoelectronic chips on a two-dimensional array of optical input and output channels carried on a single dimension of optical fibers is proposed.
Abstract: A network for multi-bit word parallel communication between optoelectronic chips on a two dimensional array of optical input and output channels carried on a single dimension of optical fibers. Each bit of a word is carried on a different wavelength and the multiple wavelengths carrying a word are wavelength multiplexed onto a single optical fiber. Multiple fibers can be joined into a one dimensional array of fibers. A transceiver for transmitting and receiving along the optical data channels comprises an array of modulators powered by individual wavelength light beams, either from individual monochromatic light sources and a light beam from a single broadband light source made to pass through a diffraction grating. The modulators are positioned so that each modulator reflects a different wavelength light beam, thereby providing multiple optical channels. Alternatively, multiple wavelengths are generated from CMOS integrated light sources. These multiple optical channels are then collimated and guided into one single mode fiber or multiple multimode fibers at its transmitting end. At the receiving end a diffraction grating is used to separate the distinct data channels by their individual wavelengths. The multiple wavelengths are then caused to fall on an array of optical detectors spaced according to the individual wavelengths to be detected. By constructing a one dimensional array of these fibers, a two dimensional array of optical data channels is realized. The size of the array is determined by the number of fibers and the number of distinct wavelengths combined in each fiber.

99 citations


Patent
18 Aug 1999
TL;DR: In this article, an optical scanning and imaging system and related method for imaging an object is described, in which an optical fiber transmits light within a predetermined wavelength from a light source through a gradient index lens which sends a collimated beam of light to the prism.
Abstract: An optical scanning and imaging system and related method for scanning and imaging an object is disclosed. The scanning and imaging system does not use mechanically moving components to achieve lateral scanning of an object. Instead, the system includes a deflecting prism comprised of a material having an index of refraction that varies with changes in an applied electromagnetic field and that remains substantially constant with changes in wavelength of incident light within a predetermined wavelength range. An optical fiber transmits light within a predetermined wavelength from a light source through a gradient index lens which sends a collimated beam of light to the prism. Due to the unique properties of the prism, the light is deflected at a substantially constant angle within a lateral scanning plane. An objective lens can be used to further focus the light exiting the prism prior to directing it on the object being imaged. A scan controller and electrodes control and modify the electromagnetic field applied to the prism such that said index of refraction also is controlled and modified. The scanning system is adapted to be used for medical imaging by disposing it within a distal end of a catheter.

94 citations


Patent
TL;DR: In this article, an arrangement for surface plasmon resonance spectroscopy (SPR) is presented, where a sample cell is associated with a sample detector and at least two sample detection areas are provided with a thin metal coating.
Abstract: The invention relates to an arrangement for surface plasmon resonance spectroscopy. The objective of the invention is to create an arrangement in a miniaturized form, whereby said arrangement is embodied as a portable unit that is economical to produce and can be used to carry out simultaneous multi-component analysis, especially with respect to interaction between bio-molecules. To achieve this aim, the inventive device consists of an optical prism (1) with a sample cell (2) associated therewith and at least two sample detection areas (21; 22) that are provided with a thin metal coating that is selected for the implementation of the SPR method and which contains, at least partially, surface-immobilized areas. Light emanating from a broadband light source (L) is conducted via an optic fiber (31) and collimated by a collimator (41) with an aperture that is adapted to the base surface of the prism, making its way to an entrance surface (11) of the optical prism (1) and a multi adpatable diaphragm (5) is provided between the collimator (41) and the entrance surface (11). Said diaphragm clears a defined optical path to the base surface (13) of the prism in a chronologically successive manner and the respective switching states thereof can be fed to an evaluation and control unit (6) via a data and control line (61) wherein current diaphragm switching states can be allocated to spectra corresponding to said switching states, whereby the spectra are obtained by detecting the light that leaves the exit surface (12) of the prism by means of another collimator (42) that is adapted to the base surface (13) of the prism in the aperture and whose exit is connected to another optic fiber (32) and the exit thereof forms the entrance to a polychromator (7) wherein the spectrally decomposed light is supplied to a CCD or diode array (71), whereby the exit thereof is connected to the evaluation and control unit (6) by means of a data line (62).

80 citations


Journal ArticleDOI
TL;DR: Circular fields could be produced with depth dose characteristics similar to those produced using conical tertiary collimators, commonly used for radiosurgery, but with a broader penumbra, and output factors for the very small fields were found to vary rapidly.
Abstract: A preliminary study of the physical characteristics of a miniature multileaf collimator (mMLC) used with 4 MV x rays is reported. The mMLC attached to the accessory mount of a class C or D Varian linear accelerator (Varian Oncology Systems, Palo Alto, CA) with a source to aperture distance of 65 cm. The field penumbra using the small leaves was found to be consistent with the anticipated field penumbra using photon jaws at the same source to aperture distance as the mMLC. The percentage depth dose values of square fields were found to be consistent with the fields collimated with the upper and lower jaws. Output factors for the very small fields were found to vary rapidly. Circular fields could be produced with depth dose characteristics similar to those produced using conical tertiary collimators, commonly used for radiosurgery, but with a broader penumbra.


Journal ArticleDOI
TL;DR: In this paper, a single narrow self-focused current jet of energetic electrons is observed to be projected into the corona nearly normal to the target, and a scaling law for the angle of the ejected electrons with incident laser intensity is given.
Abstract: Oblique incidence of a $p$-polarized laser beam on a fully ionized plasma with a low density plasma corona is investigated numerically by particle-in-cell and Vlasov simulations in two dimensions. A single narrow self-focused current jet of energetic electrons is observed to be projected into the corona nearly normal to the target. Magnetic fields enhance the penetration depth of the electrons into the corona. A scaling law for the angle of the ejected electrons with incident laser intensity is given.

Patent
22 Feb 1999
TL;DR: A vehicle lighting system includes a light source for generating light and a unitary optical element having a light collimating surface, a plurality of stepped surfaces projecting from the collimating surfaces, each stepped surface having a reflective surface angled with respect to the collimated surface for receiving collimated light, a dispersal surface angled to the stepped surfaces for dispersing collimated lights, and a kicker adjacent the surface having reflective facets adapted to receive and redirect the dispersed light as discussed by the authors.
Abstract: A vehicle lighting system includes a light source for generating light and a unitary optical element having a light collimating surface, a plurality of stepped surfaces projecting from the collimating surface, each stepped surface having a reflective surface angled with respect to the collimating surface for receiving collimated light, a dispersal surface angled with respect to the stepped surfaces, the dispersal surface having a plurality of dimples aligned with respect to the reflective surfaces for dispersing collimated light, and a kicker adjacent the surface having a plurality of reflective facets adapted to receive and redirect the dispersed light.

Journal ArticleDOI
TL;DR: An inversion algorithm that uses time-resolved transillumination measurements in the form of a sequence of picosecond-duration intensity patterns of transmitted ultrashort light pulses to reconstruct three-dimensional images of an absorbing object located inside a slab of a highly scattering medium to achieve speedy 3-D image reconstruction.
Abstract: Optical imaging and localization of objects inside a highly scattering medium, such as a tumor in the breast, is a challenging problem with many practical applications. Conventional imaging methods generally provide only two-dimensional ~2-D! images of limited spatial resolution with little diagnostic ability. Here we present an inversion algorithm that uses time-resolved transillumination measurements in the form of a sequence of picosecond-duration intensity patterns of transmitted ultrashort light pulses to reconstruct three-dimensional ~3-D! images of an absorbing object located inside a slab of a highly scattering medium. The experimental arrangement used a 3-mm-diameter collimated beam of 800-nm, 150-fs, 1-kHz repetition rate light pulses from a Ti:sapphire laser and amplifier system to illuminate one side of the slab sample. An ultrafast gated intensified camera system that provides a minimum FWHM gate width of 80 ps recorded the 2-D intensity patterns of the light transmitted through the opposite side of the slab. The gate position was varied in steps of 100 ps over a 5-ns range to obtain a sequence of 2-D transmitted light intensity patterns of both less-scattered and multiple-scattered light for image reconstruction. The inversion algorithm is based on the diffusion approximation of the radiative transfer theory for photon transport in a turbid medium. It uses a Green’s function perturbative approach under the Rytov approximation and combines a 2-D matrix inversion with a onedimensional Fourier-transform inversion to achieve speedy 3-D image reconstruction. In addition to the lateral position, the method provides information about the axial position of the object as well, whereas the 2-D reconstruction methods yield only lateral position. © 1999 Optical Society of America OCIS codes: 100.3190, 170.3010, 170.3880, 170.6920, 290.7050.

Patent
14 Jan 1999
TL;DR: A point-scanning luminescent microscope as discussed by the authors has at least one collimated light source, an optical arrangement which focuses the light of the excitation light source on an object to be studied, a detector arrangement for acquiring light emitted by the object, and a scanner arrangement which causes relative movement between the scanning light beam and the object in at least two directions.
Abstract: A point-scanning luminescent microscope, especially for studying biological objects, has at least one collimated light source for producing an excitation light beam, an optical arrangement which focuses the light of the excitation light source on an object to be studied, at least one detector arrangement for acquiring light emitted by the object, an optical arrangement which collects the light emitted by the object and supplies it to the detector arrangement, and a scanner arrangement which causes relative movement between the scanning light beam and the object in at least two directions. The scanner arrangement has piezoactuators for achieving scanning movements between the scanning light beam and object. The detector arrangement can have a surface sensor which forms a confocal diaphragm. The light source can be designed to deliver rectangular pulses. When the microscope is designed for twin-photon fluorescent microscopy, an objective lens is provided for illuminating the object and can be is used, at the same time, for collecting some of the photons emitted by the object, and a second detector is provided behind a condenser lens of the objective lens.

Journal ArticleDOI
TL;DR: The optimization of a conventional treatment head for use of multileaf collimated electron beams based on Monte Carlo calculations using the software package BEAM found the beam characteristics for some of these designs were found to fulfil the criteria for clinically useful beams down to at least 9 MeV.
Abstract: This paper describes how a conventional treatment head can be modified for use of multileaf collimated electron beams. Automatic and dynamic beam delivery are possible for both electrons and photons by using the computer controlled multileaf collimator (MLC) for both photon and electron beams. Thereby, the electron beams can be mixed more freely into the treatment to take advantage of the specific depth modulation characteristics of electrons. The investigation was based on Monte Carlo calculations using the software package BEAM. The physical parameters used in this optimization were the beam penumbra and the virtual/effective point source position. These parameters are essential for shaping beams, beam matching and for dosimetry calculations. The optimization was carried out by modifying a number of parameters: replacing the air atmosphere in the treatment head with helium, adding a helium bag below the MLC, changing the position of the scattering foils, modifying the monitor chamber, and adjusting the position of the MLC. The beam characteristics for some of these designs were found to fulfil our criteria for clinically useful beams down to at least 9 MeV.

Patent
Kiichi Ueyanagi1, Baba Kazuo1
19 Mar 1999
TL;DR: An optical head which implements high recording density of a recording medium and which is miniaturized in size and improved in data transfer rate, a disk apparatus, and a method for manufacturing the optical head are provided in this article.
Abstract: An optical head which implements high recording density of a recording medium and which is miniaturized in size and improved in data transfer rate, a disk apparatus, and a method for manufacturing the optical head are provided. A laser beam is emitted from a semiconductor laser, the laser beam is collimated by the collimator lens to a collimated beam and reflected by a mirror, condensed by an condense lens, and incident to an incident surface of a transparent condensing medium. The condensed beam which was incident to the incident surface is refracted by the incident surface, the refracted beam is condensed on a condense surface, a beam spot is formed on the condense surface, and a near field wave leaks from a small aperture. The near field wave leaked from the small aperture propagates in a recording layer of a recording. The beam is served for recording/reproduction on the recording layer.

Patent
Hiroyoshi Funato1
24 Aug 1999
TL;DR: In this article, a holographic optical element receives a reflection beam of the light spot from one of the first and second optical disks and provides holographic effects on the reflection beam so as to diffract the reflectionbeam in predetermined diffracting directions depending on the wavelength of the reflection beacon.
Abstract: An optical pickup apparatus includes first and second light sources which selectively emit one of first and second light beams, the first and second light beams being different in wavelength, the wavelengths of the first and second light beams being appropriate for accessing first and second optical disks respectively. A coupling lens converts a corresponding one of the first and second light beams into a collimated beam. An objective lens forms a light spot on a corresponding one of the first and second optical disks by focusing the collimated beam. A holographic optical element receives a reflection beam of the light spot from one of the first and second optical disks and provides holographic effects on the reflection beam so as to diffract the reflection beam in predetermined diffracting directions depending on the wavelength of the reflection beam. A photodetector receives the reflection beam from the holographic optical element at light receiving areas and outputs signals indicative of respective intensities of the received reflection beam at the light receiving areas, so that a focusing error signal and a tracking error signal are generated based on the signals.

Patent
26 Feb 1999
TL;DR: In this paper, a geometric beamplitter is used to reflect one of the collimated exitation and emission radiation such that the emission is directed to a detector and the collimating exitation is directed away from the detector.
Abstract: An imaging system comprises three or more sources for providing excitation radiation of different wavelengths, an objective lens for focusing one or more of the exitation wavelengths onto a sample to produce fluorescent emission, and a mirror, configured as a geometric beamsplitter, disposed in the transmission path of the emission radiation and excitation radiation subsequent to reflection from the sample and collimation by the lens, wherein the mirror is utilized to reflect one of the collimated exitation and emission radiation such that the emission is directed to a detector and the collimated exitation is directed away from the detector.

Patent
08 Jul 1999
TL;DR: In this paper, the authors present a scanner with collimated pulsed electromagnetic radiation in the form of a scanning beam, a receiver of light pulses reflected from a monitored sector, and an evaluation unit which determines relative coordinates of objects from transition times and angles of pulses.
Abstract: The scanner has a transmitter of collimated pulsed electromagnetic radiation in the form of a scanning beam, a receiver of light pulses reflected from a monitored sector, and an evaluation unit which determines relative coordinates of objects from transition times and angles of pulses. The transmitter is rotated about an axis by a motor drive. Several synchronously rotated transmitters can be used. An Independent claim is also included for an arrangement for the optical detection of obstructions.

Patent
08 Apr 1999
TL;DR: A light pattern controller provides a pattern of light to a collimator as mentioned in this paper, where the pattern is collimated and reflected such that it is substantially parallel to the optical axis of an imaging system.
Abstract: A light pattern controller provides a pattern of light to a collimator. The light pattern controller includes a beam deflector that sweeps a circular pattern with a radius that is directly proportional to the rotational speed of the beam deflector. Alternatively, the light pattern controller includes a two-dimensional scanning galvanometer that sweeps out the circular pattern or a liquid crystal shutter. The pattern of light is collimated and reflected such that it is substantially parallel to the optical axis of an imaging system. A focusing element redirects the collimated light pattern onto a sample part at an angle of incidence which is a function of the radius of the light column.

Patent
Kenji Nishi1, Toru Kiuchi1
18 Oct 1999
TL;DR: In this article, a reflective member is fixedly or movably provided near the pupil plane of a projection optical system with which a projection exposure apparatus is equipped, and a collimated measuring beam with an exposure wavelength is incident from the object plane side or image plane side of the projector.
Abstract: A reflective member is fixedly or movably provided near the pupil plane of a projection optical system with which a projection exposure apparatus is equipped. A collimated measuring beam with an exposure wavelength is incident from the object plane side or image plane side of the projection optical system, and the intensity of the beam reflected by the reflective member is detected photoelectrically to measure a value corresponding to the attenuation factor (transmissivity or reflectivity) of the projection optical system or the variation with time of the attenuation factor (transmissivity or reflectivity) of the projection optical system. In accordance with the measurement results, the exposing conditions when a photosensitive substrate is exposed are corrected to avoid the deterioration of the exposure control precision due to the variation of the attenuation factor (transmissivity variation or reflectivity variation) which is caused in the projection optical system and illumination optical system of a projection exposure apparatus which uses ultraviolet illumination light.

Patent
12 Nov 1999
TL;DR: In this article, a system which is preferably employed in a laser alignment instrument produces up to five orthogonal beams from a single laser diode beam, taking advantage of the elliptical shape of the beam.
Abstract: A system which is preferably employed in a laser alignment instrument produces up to five orthogonal beams from a single laser diode beam. In one embodiment the optics take advantage of the elliptical shape of the beam from a laser diode which when collimated produces a plurality of orthogonal beams by reflection off a plurality of 45°-angled reflective surfaces intercepting outer portions of the beam. In one preferred embodiment a solid reflective element was four 45°-angled facets to produce four beams from outer portions of a preferably non-elliptical beam, and a fifth orthogonal beam is produced by transmission of a central portion of the beam through the element. The element can be solid glass, or it can be glass or other material with a central hole.

Patent
27 May 1999
TL;DR: In this paper, a method and apparatus for converting a beam of light that is substantially coherent and has a coherence length into substantially incoherent radiation was proposed, which is based on collimating the beam, delaying a first portion of the beam by a first optical delay by ballistic passage through a first cell of an optical element, and delaying each of a plurality of other portions of the beacons by an optical delay different from the first optical delays by an amount exceeding the coherent length of the beacon.
Abstract: A method and apparatus for converting a beam of light that is substantially coherent and has a coherence length into substantially incoherent radiation The method has the steps of collimating the beam, delaying a first portion of the beam by a first optical delay by ballistic passage through a first cell of an optical element, and delaying each of a plurality of other portions of the beam by an optical delay different from the first optical delay by an amount exceeding the coherence length of the beam

Patent
30 Nov 1999
TL;DR: In this article, a lighting assembly consisting of a light source means and a collimating means for substantially collimating the light from the source is described. And the light direction modifying means includes a large plurality of prisms on the outer surface thereof, arranged so that the radii of several adjacent ones substantially meet at a point, thereby forming a wave lens.
Abstract: A lighting assembly which includes light source means and collimating means for substantially collimating the light from the source. There are transmission means for transmitting the substantially collimated light to a point remote from the collimating means, and, in one arrangement, having an upper section which allows transmission of light therethrough and a lower section which reflects light. Light direction modifying means such as a lens or a reflector is located in the transmission means and remote from the collimating means for receiving light from the collimating means and modifying the direction of the light to pass outside of the transmission means through the light-transmitting section. The light direction modifying means includes a large plurality of prisms on the outer surface thereof. The prisms may be arranged so that the radii of several adjacent ones substantially meet at a point, thereby to form a “wave” lens.

Patent
David J. Aziz1, Bryan W. Guenther1
30 Nov 1999
TL;DR: In this paper, a laser interferometer is embedded into an interference microscope to precisely determine the in-focus position of the microscope objective's reference mirror, which is then used to produce interference fringes.
Abstract: A laser interferometer is embedded into an interference microscope to precisely determine the in-focus position of the microscope objective's reference mirror. A collimated laser beam is introduced into the microscope system and split into two beams directed toward a calibration reference surface and the interference objective. The light reflected from the calibration reference surface is returned to the camera. The light into the interference objective is focused onto the reference mirror and returned to the camera. For the purpose of calibration, the two beams are combined at the camera to produce interference fringes. When the reference mirror is in focus, the returned beam is collimated; if the mirror is on either side of focus, the beam is either converging or diverging. Accordingly, the interferogram produced at the camera reflects the in-focus or out-of-focus condition of the reference mirror. The curvature of the wavefront returned from the reference mirror is determined electronically by analyzing the interference fringes produced with the beam returned from the calibration reference surface. By minimizing the curvature of the reference-mirror wavefront as the mirror is translated along the optical path, the reference mirror can be focused with an accuracy greater than possible by visual observation. Furthermore, by automating the focusing system with a precise translation mechanism driven by closed-loop control, operator-to-operator variations are completely eliminated.

Journal ArticleDOI
TL;DR: Results show that the newly proposed long-range nondiffracting beam (LRNB) is much less influenced by atmospheric turbulence than other beams and suggest that the LRNB can apply to many fields.
Abstract: A narrow light beam that propagates in the atmosphere with less disturbance than conventional light beams is introduced. The operating method and features of the newly proposed long-range nondiffracting beam (LRNB) are briefly demonstrated. Some experimental results of the atmospheric propagation of this beam at a distance of 500 m are shown in comparison with a conventional collimated beam and a focused beam. The results and related analyses show that the LRNB is much less influenced by atmospheric turbulence than other beams and suggest that the LRNB can apply to many fields.

Patent
03 Mar 1999
TL;DR: In this article, an optical illumination system comprising a waveguide (16) that accepts light and transmits the light via total internal reflection is described. But this system is not suitable for indoor applications.
Abstract: An optical illumination system (2) comprising a waveguide (16) that accepts light and transmits the light via total internal reflection. Attached on one face of the waveguide (16) is an array of lenticular microprisms (28), with each microprism (28) having a light input surface (30) optically coupled to the waveguide (16) and a light output surface (32). The light input surface (30) is defined by a number of tapered grooves (34) which prevent light from escaping form the waveguide (16) and further redirect light within the microprism (28). Light that escapes from the waveguide (16), reflects off the tilted sidewalls (36, 38) of the tapered grooves (34) and emerges from the microprism (28) as a spatially directed light source. An array of lenticular microlenses (60) may be positioned to accept the output of the microprisms (28) so that the light exiting from the microlenses (60) is a substantially collimated light source.

Journal ArticleDOI
TL;DR: The calculated OPF for the 4 mm collimator helmet was more than 8% higher than the value currently used, but in good agreement with the average of experimental values obtained by various Gamma Knife centres throughout the world and with the value now recommended by the manufacturer, Elekta.
Abstract: The Leksell Gamma Knife is a standard radiosurgical tool for treating brain lesions by directing beams of gamma radiation to a specific region. The diameter of the gamma beams is confined by collimator systems and available collimator sizes are 4, 8, 14 and 18 mm. The reduction in dose rate for each collimator helmet is called the output factor (OPF). Experimental determination of OPFs is difficult due to the extremely narrow beams for which the dose is determined. In the present work, the PRESTA version of the EGS4 Monte Carlo code was used to obtain relative OPFs for the Leksell Gamma Knife for collimator sizes of 14, 8 and 4 mm (relative to that of the 18 mm collimator). A spherical probe with a radius of 1 mm was utilized in this computer experiment. Our Monte Carlo results gave OPFs of 0.974, 0.951 and 0.872 for the 14 mm, 8 mm and 4 mm collimators respectively, relative to the 18 mm collimator. Our calculated OPF for the 4 mm collimator helmet was more than 8% higher than the value currently used, but in good agreement with the average of experimental values obtained by various Gamma Knife centres throughout the world and with the value now recommended by the manufacturer, Elekta (Elekta Instrument AB, Skeppargatan 8, S-114 52 Stockholm, Sweden).