scispace - formally typeset
Search or ask a question

Showing papers on "Collimated light published in 1996"


Journal ArticleDOI
TL;DR: A new method of dosimetry of ionizing radiations has been developed that makes use of tissue-equivalent polymer gels which are capable of recording three-dimensional dose distributions, including measurements of the complex distributions produced by multi-leaf collimators, dynamic wedge and stereotactic treatments, and for quality assurance procedures.
Abstract: A new method of dosimetry of ionizing radiations has been developed that makes use of tissue-equivalent polymer gels which are capable of recording three-dimensional dose distributions. The dosimetric data stored within the gels are measured using optical tomographic densitometry. The dose-response mechanism relies on the production of light scattering micro-particles which result from the polymerization of acrylic comonomers dispersed in the gel. The attenuation of a collimated light beam caused by scattering in the irradiated optically turbid medium is directly related to the radiation dose over the range 0 - 10 Gy. An optical scanner has been developed which incorporates an He - Ne laser, photodiode detectors, and a rotating gel platform. Using mirrors mounted on a translating stage, the laser beam scans across the gel between each incremental rotation of the platform. Using the set of optical density projections obtained, a cross sectional image of the radiation field is then reconstructed. Doses in the range 0 - 10 Gy can be measured to better than 5% accuracy with a spatial resolution of approximately 2 mm using the current prototype scanner. This method can be used for the determination of three-dimensional dose distributions in irradiated gels, including measurements of the complex distributions produced by multi-leaf collimators, dynamic wedge and stereotactic treatments, and for quality assurance procedures.

339 citations


Journal ArticleDOI
TL;DR: The Nuclear Resonance Beamline at ESRF as discussed by the authors is dedicated to the excitation of nuclear levels by synchrotron radiation and is optimized to provide an intense, highly monochromatic, collimated and stable X-ray beam of small cross-section at the Mossbauer transition energies between 6 and 30 keV.
Abstract: The Nuclear Resonance Beamline at ESRF is dedicated to the excitation of nuclear levels by synchrotron radiation. The sources of radiation and optical elements are optimized to provide an intense, highly monochromatic, collimated and stable X-ray beam of small cross-section at the Mossbauer transition energies between 6 and 30 keV. The set-up of the beamline allows to perform studies in diffraction, small angle scattering, forward scattering and incoherent scattering. Equipment is available to maintain the sample at variable temperature and magnetic field. Fast detectors and timing electronics serve to separate the delayed nuclear scattering from the “prompt” electronic scattering and to measure the time spectra of nuclear radiation with sub-nanosecond resolution. The general lay-out and the parameters of the beamline are reported. Typical domains of applications are discussed and illustrated by first experimental results.

314 citations


Journal ArticleDOI
26 Jul 1996-Science
TL;DR: Electron acceleration and the appearance of high-frequency modulations in the transmitted light spectrum were both found to have sharp thresholds in laser power and plasma density.
Abstract: When a terawatt-peak-power laser beam is focused into a gas jet, an electron plasma wave, driven by forward Raman scattering, is observed to accelerate a naturally collimated beam of electrons to relativistic energies (up to 10 9 total electrons, with an energy distribution maximizing at 2 megaelectron volts, a transverse emittance as low as 1 millimeter-milliradian, and a field gradient of up to 2 gigaelectron volts per centimeter). Electron acceleration and the appearance of high-frequency modulations in the transmitted light spectrum were both found to have sharp thresholds in laser power and plasma density. A hole in the center of the electron beam may indicate that plasma electrons were expelled radially.

299 citations


Patent
05 Jan 1996
TL;DR: A light expanding system for converting a light beam generated from a point-like light source into a collimated linear or planar light beam is described in this article, which is suitable for use in devices utilizing a linear light beam, such as a scanner.
Abstract: A light expanding system for converting a light beam generated from a point-like light source into a collimated linear or planar light beam is disclosed herein. According to an embodiment of the invention, a system for producing a linear light beam includes a beam collector and a light pipe adjacent to which a multiplicity of specially configured microprisms are located. The light expanding system according to this embodiment is suitable for use in devices utilizing a linear light beam, such as a scanner. According to another embodiment of the invention, a system for producing a planar light beam includes, in addition to the beam collector and light pipe described above, an additional light pipe with adjacent microprisms. The light expanding system according to this embodiment of the invention can be used, for example, in displays, road signs, medical research equipment, instrument meters or jewelry; to light pictures or art work; or as part of a see-through lighting system for use in dentistry and surgery.

274 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used combined null and off-null ellipsometry at an incident angle close to the pseudo-Brewster angle of a high index substrate such as silicon.
Abstract: Imaging ellipsometry is presented as a technique for quantification and visualization of the lateral thickness distribution of thin (0–30 nm) transparent layers on solid substrates. The main advantage of imaging ellipsometry is that every point on a surface is measured at the same time with a high lateral resolution. The method is based on the use of combined null and off‐null ellipsometry at an incident angle close to the pseudo‐Brewster angle of a high index substrate such as silicon. In the present experimental setup, a xenon lamp, a collimator, and a wavelength‐selective filter provide an expanded collimated probe beam with a diameter of 25 mm. Other major components in the system are a polarizer, a compensator, and an analyzer. In this way, a 15×30 mm2 image of a sample surface can be focused onto a charge‐coupled‐device video camera and transferred to a computer for further evaluation by image processing. Thickness measurements are performed for calibration purposes with ordinary null ellipsometry. ...

199 citations


Proceedings ArticleDOI
06 Dec 1996
TL;DR: Theoretical and computer modeling approaches, such as Mie theory, radiative transfer theory, diffusion wave correlation spectroscopy, Monte Carlo simulation method were applied for tissue optics analysis in a process of its clearance as discussed by the authors.
Abstract: Theoretical and computer modeling approaches, such as Mie theory, radiative transfer theory, diffusion wave correlation spectroscopy, Monte Carlo simulation method were applied for tissue optics analysis in a process of its clearance. CW collimated transmittance and forward scattering measurements as well as intensity correlation experiments were used for tissue structure and optical properties monitoring. Conrolled tissue samples of the human sclera were taken. A chemical applicator-conrollers Trazograph, glucose and polyethileneglycol solutions were used. On the base of sclera samples clearance investigation the general principles of tissue optical and structural parameters controlling were established.

197 citations


Patent
10 Jun 1996
TL;DR: In this paper, a continuous, variable thickness, multi-cavity interference filter extends on the multiport surface of the optical block over the multiple ports, and the continuous interference filter transmits a different wavelength sub-range of the multiple wavelength collimated light passed by the optical port, and reflects other wavelengths.
Abstract: An optical multiplexing device spatially disburses collimated light from a fiber optic waveguide into individual wavelength bands, or multiplexes such individual wavelength bands to a common fiber optic waveguide or other destination. The optical multiplexing device has application for dense channel wavelength division multiplexing (WDM) systems for fiber optic telecommunications, as well as compact optical instrument design. Multiple wavelength light traveling in a fiber optic waveguide is separated into multiple narrow spectral bands directed to individual fiber optic carriers or detectors. An optical block has an optical port for passing the aforesaid multiple wavelength collimated light, and multiple ports arrayed in spaced relation to each other along a multiport surface of the optical block. A continuous, variable thickness, multi-cavity interference filter extends on the multiport surface of the optical block over the aforesaid multiple ports. At each of the multiple ports the continuous interference filter transmits a different wavelength sub-range of the multiple wavelength collimated light passed by the optical port, and reflects other wavelengths. Multicolor light passed to the optical block from the optical port is directed to a first one of the multiple ports on an opposite surface of the optical block. The wavelength sub-range which is "in-band" of such first one of the multiple ports is transmitted through that port by the local portion of the continuous, variable thickness interference filter there, and all other wavelengths are reflected. The light not transmitted through the first port is reflected to strike a second port, at which a second (different) wavelength band is transmitted and all other light again reflected. The reflected optical signals thus cascades in a "multiple-bounce" sequence down the optical block of the multiplexing device, sequentially removing each channel of the multiplexed signal. In reverse operation, individual channels are combined in the optical block and transmitted through the optical port.

192 citations


Patent
08 Oct 1996
TL;DR: In this article, a light pipe with a set of specially configured microprisms is used to rotate the divergent angle of light for frontlighting or backlighting a display or other such arrangement requiring front lighting or back lighting.
Abstract: An assembly for frontlighting or backlighting a display or other such arrangement requiring frontlighting or backlighting is disclosed herein. The assembly uses a light pipe with a set of specially configured microprisms to rotate the divergent angle of light. The divergent angle rotator is used with a flat collimator assembly for efficient display illuminating with light of a controllable degree of collimation in both dimensions.

158 citations


Patent
02 Feb 1996
TL;DR: In this article, a method and apparatus for high resolution breast imaging using collimated non-ionizing acoustic radiation and electromagnetic radiation in the near ultraviolet, visible, infrared and microwave regions (i.e. "light") rather than ionizing x-radiation was presented.
Abstract: The present invention provides a method and apparatus for high resolution breast imaging using collimated non-ionizing acoustic radiation and electromagnetic radiation in the near ultraviolet, visible, infrared and microwave regions (i.e. "light") rather than ionizing x-radiation. The light used is of a narrow spectral bandwidth in that the optical properties of interest are relatively uniform over the bandwidth. The incident collimated light is transmitted through and backscattered out of a breast. Normal and diseased breast materials exhibit comparatively distinct characteristics when exposed to radiation and are thereby differentiated. Collimation can also be used to control the level of scattered radiation. Radiation coupling materials can be employed during image acquisition to enhance radiation coupling into and out of the breast as well as providing desirable absorption and scattering properties. Additional scatter reduction and/or improved sensitivity can be attained by compressing a region of the breast using contoured and/or flat compression plates of various sizes which may include an open region allowing access to the surface of the breast for irradiating a portion of the breast. An acoustic field can be introduced into a volume of breast tissue altering its optical qualities. These changes can be recorded by intersecting an optical field with the acoustic field, providing spatial information and tissue characterization.

153 citations


Patent
Ronald T. Smith1
02 Oct 1996
TL;DR: In this article, a holographic thin rear exterior lamp for a vehicle including a light pipe (11) having first and second opposing surfaces (11a, 11b) having a light source (17, 19) for providing a substantially collimated beam, a transmission hologram (15) disposed on one of the first two surfaces of the light pipe such that a portion of the substantiallycollimated light propagates by total internal reflection within the lightpipe, the rear exterior lamps hologram and the polarization rotating retarder film.
Abstract: A holographic thin rear exterior lamp for a vehicle including a light pipe (11) having first and second opposing surfaces (11a, 11b), a rear exterior lamp hologram (13, 113) attached to one of the first and second surfaces of the light pipe, a polarization rotating retarder film (16, 116) attached to one of the first and second opposing surfaces oppositely from the rear exterior lamp hologram, a light source (17, 19) for providing a substantially collimated beam, a transmission hologram (15) disposed on one of the first and second surfaces of the light pipe for coupling the substantially collimated beam into the light pipe such that a portion of the substantially collimated light propagates by total internal reflection within the light pipe, the rear exterior lamp hologram and the polarization rotating retarder film The polarization rotating retarder film is configured to impart a substantially halfwave retardance to internally reflected light that passes twice therethrough

126 citations


Patent
09 Apr 1996
TL;DR: In this paper, an LED point imaging scanner for stimulating and reading fluorescent and reflective signal radiation from a target sample (10) is disclosed, where an LED light source (12) is mounted on scan head (20) and focused into pinhole aperture (15) of spatial filter (30), then collimated and focused to a spot (17) on sample(10), the spatial filter or an optical fiber equivalent, effectively restricts the incoherent LED light and creates a point light source.
Abstract: An LED point imaging scanner for stimulating and reading fluorescent and reflective signal radiation from a target sample (10) is disclosed. LED light source (12) is mounted on scan head (20) and focused into pinhole aperture (15) of spatial filter (30), then collimated and focused to a spot (17) on sample (10). The spatial filter, or an optical fiber equivalent, effectively restricts the incoherent LED light and creates a point light source. Signal radiation from sample (10) is collected through scan head (20) and the returning light beam is collimated and focused onto detection means (40). A spatial filter (22) in the path of the returning beam may also be utilized. Detection means (40) is either a small detector directly mounted onto the scan head, or an end of an optical fiber which transmits the point image to a remotely-positioned stationary detector. The scan head is moved along one or two axes relative to the sample.

Patent
04 Apr 1996
TL;DR: In this article, a method and device for acquiring data related to topography of a medium includes projecting light, allowably from more than one direction, onto the surface of the medium at an angle of less than sixteen degrees relative to the surface and imaging the surface.
Abstract: A method and device for acquiring data related to topography of a medium includes projecting light, allowably from more than one direction, onto the surface of the medium at an angle of less than sixteen degrees relative to the surface and imaging the surface. For example, the imaging sensor may be an array of sensor elements that is used to determine navigation of a hand-held scanner along an original. By introducing light at an angle of less than sixteen degrees, surface irregularities cast shadows that form a high contrast illumination pattern along the surface of the medium. The navigation sensor detects multi-element variations of intensity of scattered light from the surface with respect to positions along the surface, so that the Nyquist criteria are adequately satisfied. Typically, the light is collimated incoherent light, but this is not critical. The illumination angle can be established by using a prism. The prism may have an antireflective thin film coating on one or more prism faces. The employment of a prism provides a number of advantages, such as use of a transparent surface in contact with the media and raising the illumination source(s) away from the media.

Patent
Gordon A. Thomas1
31 Jul 1996
TL;DR: In this paper, an optical identification system includes a light source with a broad wavelength spectrum that is directed on an object to be identified, and a set of known spectra determine the reference spectra and the unknown test spectrum is compared with the reference sets.
Abstract: An optical identification system includes a light source with a broad wavelength spectrum that is directed on an object to be identified. Suitable optical components, such as, one or more collimating lenses gather light that is reflected from the object and direct this light into a spectrometer. The spectrometer disperses the collimated light using a dispersing element, such as one or more gratings, prisms or a combinations of both, onto an array of detectors. The array of detectors may be comprised of a linear diode array or a charge-coupled device (CCD) array which indicates the amount of light at each of a finely-spaced set of wavelengths covering a wide spectral range. The detectors are sensitive over a wavelength region, for example, in the case of silicon detectors from near-infrared plus the visible region, e.g., from 250 nm to 1100 nm. The set of signals from the detectors is read with an analog to digital converter, and transferred to a computer in the form of a spectrum. A set of known spectra determine the reference spectra and the unknown test spectrum is compared with the reference sets. A software program in the computer compares the test spectrum with reference spectra sets utilizing a statistical program. The program takes into account how much the known spectra vary from one another in addition to the average values. A display reads out a list of possible matches in rank order that have a probability of match greater than a predetermined threshold. An operator checks that the first listed item is correct and either accepts the first choice or indicates the correct choice. As an alternative, the system could automatically accept the first choice.

Patent
28 Aug 1996
TL;DR: In this paper, a diffused light reflectance readhead is described, which employs an improved light emitting diode (LED) providing a more strongly collimated beam of light around a beam axis onto a reagent test pad.
Abstract: A diffused light reflectance readhead is disclosed. The readhead employs an improved light emitting diode (LED) providing a more strongly collimated beam of light around a beam axis onto a reagent test pad. The reagent test pad is supported on a strip guide at an angle .alpha. of 5 degrees with respect to the perpendicular of the beam axis. It has been discovered that when .alpha. is between 3 and 8 degrees that specular reflection is dramatically reduced in relation to the small reduction in reflected light received by a sensor. The diffuse reflected light travels to the sensor by passing through a staircase optical baffle at an angle of 45 degrees to the perpendicular of the beam axis. The sensor converts the optical signal into an electrical one for processing and analysis. One embodiment of the present invention can detect the presence of glucose in a blood sample.

Patent
Martin C. Nuss1
09 Sep 1996
TL;DR: In this paper, an optical system constructed in accordance with an illustrative embodiment of the present invention comprises a source for emitting radiation in a range of frequencies within from 100 GHz to 20 GHz, a coupling lens structure for coupling radiation emitted by said source into free space, at least one collimating optical element for collimating received coupled radiation into a beam having a substantially frequency independent diameter and substantially no wavefront curvature, and a detector for detecting the beam collimated by the at least collimating element.
Abstract: Optical system architectures with improved spatial resolution are provided in which the radiation useful for THz spectroscopy and other investigative procedures can be directionally coupled, in a highly efficient manner, into and out of photoconductive structures such, for example, as dipole antennas. An optical system constructed in accordance with an illustrative embodiment of the present invention comprises a source for emitting radiation in a range of frequencies within from 100 GHz to 20 THz, a coupling lens structure for coupling radiation emitted by said source into free space, at least one collimating optical element for collimating received coupled radiation into a beam having a substantially frequency independent diameter and substantially no wavefront curvature, and a detector for detecting the beam collimated by the at least one collimating optical element. In an optical system constructed in accordance with another embodiment of the present invention, a modified substrate lens structure is used and the collimating optical element is replaced by at least one optical element that focuses received coupled radiation onto a diffraction limited focal spot on or within the medium under investigation.

Journal ArticleDOI
TL;DR: In this article, a noncontact optical microtopographer based on an active, discrete triangulation procedure has been under development for some time at the physics department of the University of Minho.
Abstract: A noncontact optical microtopographer based on an active, discrete triangulation procedure has been under development for some time at the physics department of the University of Minho. Our experi- ence has shown that this kind of triangulation-based surface inspection system can be applied, not only to long-distance range sensing, but also to smaller samples or other surfaces with height resolutions that can go down to the submicron range. In our system, the topographic information is obtained from the horizontal shift of the bright spot created by an oblique collimated light beam on a surface when it is displaced vertically. A laser beam is focused onto a small, diffraction-limited spot on the surface and is made to scan it over the desired region. The horizontal position of the bright spot is perpendicularly imaged onto a linescan cam- era and the information on the individual detectors that are activated, above a certain controllable intensity threshold level, is used to compute the corresponding horizontal spot's shift on the reference plane. Thus we can compute the distance between the surface and a reference plane at each sampled point. A map of the surface topography can then be built and statistical surface characterization parameters may be calculated. Our versatile laboratory setups have been used for different inspection tasks such as thickness measurements and relief mapping of different kinds of films (polyethylene, thin sputtered copper, tin dioxide and silver films) and several kinds of fabrics, and roughness measure and topo- graphic inspection of polyethylene molds and graphite samples. In this communication we briefly describe our method. The current configura- tion of our laboratory setup is described. A hand-held version of our system and also the setup for long-distance dimensional assessments are briefly presented. © 1996 Society of Photo-Optical Instrumentation Engineers. Subject terms: rough surfaces; microtopography; electro-optical sensors; rough- ness.

Journal ArticleDOI
TL;DR: Numerical tests and experimental results from a phantom material as well as samples of biological tissue confirmed the feasibility of applying the Monte Carlo method with the small-angle approximation of the radiative transfer theory to the determination of the optical properties of turbid media.
Abstract: We have combined the Monte Carlo method with the small-angle approximation of the radiative transfer theory to derive the optical properties (the absorption coefficient, the scattering coefficient, and the anisotropy factor) of turbid materials from integrating-sphere measurements (the total transmittance and the diffuse reflectance) and the collimated transmittance. Unlike one-dimensional models, the technique accounts for the side losses of light at the edges of the sample. In addition, it enables the correction of the measured collimated signal for the contribution of multiply scattered light. On the other hand, the hybrid technique allows a significant reduction in calculation time compared with inverse methods based on a pure Monte Carlo technique. Numerical tests and experimental results from a phantom material (milk) as well as samples of biological tissue (porcine myocardium) confirmed the feasibility of applying this technique to the determination of the optical properties of turbid media.

Patent
TL;DR: In this paper, a laser system for use in performing dental procedures is provided, which includes a handpiece which is capable of being connected to a source of laser light, such as a fiber optic cable.
Abstract: A laser system for use in performing dental procedures is provided. The system includes a handpiece which is capable of being connected to a source of laser light, such as a fiber optic cable. The fiber optic capable carries laser light into the handpiece. For most of the purposes contemplated herein, the argon laser light is preferred. The handpiece includes a collimating lens such that the laser light is collimated and a collimated laser output exits said handpiece. Collimated laser light is found to be useful in initiating the curing of dental resin restorative materials. Also placed within the handpiece is a mirror for controlling the direction of laser light output from said handpiece and for directing the collimated laser light toward a dental work area. Finally, multiple detachable attachments are provided which are capable of being mounted on the exterior or at the proximal end of said handpiece for optionally modifying said collimated laser light output. Such attachments may include lenses, optical filters, and fiber optic cables.

Patent
David R. Miers1
30 Jul 1996
TL;DR: In this article, a beam shaping aperture is inserted between the spatial filter and the focussing lens to shape the laser beam, which is a rectangular aperture having a height to width ratio in a range of from 3:1 to 5:1 such that each dimension is on the order of hundreds of micrometers.
Abstract: An optical illuminator assembly for an analytical instrument, such as a clinical hematology or a flow cytometer instrument, including a laser diode having a diverging laser beam output, a collimating lens to collimate the diverging laser beam, a spatial filter operating on the collimated laser beam to spatially filter the beam, and a focussing lens to focus the spatially filtered beam into a flow cell containing particles suspended in a moving stream. A beam shaping aperture is preferably inserted between the spatial filter and the focussing lens to shape the laser beam. The spatial filter preferably includes an objective lens, a collimating lens, and a filter aperture interposed between the objective and imaging lenses. The filter aperture is preferably rectangular, having a height to width ratio in the range of 1:2 to 1:3 such that each dimension is on the order of tens of micrometers. The beam shaping aperture is preferably a rectangular aperture having a height to width ratio in a range of from 3:1 to 5:1 such that each dimension is on the order of hundreds of micrometers.

Patent
David R. Miers1
30 Jul 1996
TL;DR: In this paper, a light scatter detector assembly for an analytical instrument, such as a laser flow cytometer or clinical hematology instrument having at least two angles of scatter, is presented.
Abstract: A light scatter detector assembly for an analytical instrument, such as a laser flow cytometer or clinical hematology instrument having at least two angles of scatter. A high numerical aperture lens system is used, preferably a system using only two lenses to collect light after interacting with suspended particles passing through a flow cell into a collimated beam. A dark stop having apertures in different locations is interposed in the collimated beam light detected to produce therefrom two optical beams, respectively corresponding to the two scatter signals, e.g., high angle scatter and low angle scatter. The apertures are preferably radial sectors. The two scatter beams are passed to a beam separating element and through a collimating lens onto respective photodetectors. The beam separating element may be a split mirror having two mirrors mounted at an angle to each other, e.g., less than 15°, preferably 51/2°, to direct the beams in different directions to the two photodetectors. Alternatively, the beam separating element may be a multifaceted prism having at least two refracting portions to direct the two beam outputs to different photodetectors. The same lens may be used to pass the beams directed in different directions by the beam separating element to the two different photodetectors. The two photodetectors are preferably mounted on a single printed circuit board (pcb) in a prealigned manner using conventional pcb component mounting technology.

Patent
14 Nov 1996
TL;DR: A liquid crystal display apparatus includes a liquid crystal device, an illumination device for irradiating the device with collimated light, and a control device for electrically controlling a direction of travel of light going out from or entering the device as discussed by the authors.
Abstract: A liquid crystal display apparatus includes: a liquid crystal display device; an illumination device for irradiating the liquid crystal display device with collimated light; and a control device for electrically controlling a direction of travel of light going out from or entering the liquid crystal display device, thereby having adjustable viewing angle characteristics.

Patent
20 Jun 1996
TL;DR: In this paper, a modulated source of radiation, which directs radiation toward a scene, telecentric optics which receive and collimate radiation reflected from the scene, and a detector which detects an image formed from the modulated collimated radiation; and a processor which forms an image having an intensity value distribution indicative of the distance of objects from the apparatus, responsive to the intensity distribution of the detected image.
Abstract: Apparatus for creating an image indicating distances to objects in a scene, comprising: a modulated source of radiation, which directs radiation toward a scene; telecentric optics, which receive and collimate radiation reflected from the scene; a modulator, which modulates the collimated radiation; a detector which detects an image formed from the modulated collimated radiation; and a processor, which forms an image having an intensity value distribution indicative of the distance of objects from the apparatus, responsive to the intensity distribution of the detected image.

Patent
10 Jul 1996
TL;DR: In this article, an optically-based position location system, consisting of multiple reflectors positioned at known locations in an environment, is presented. But the system is not suitable for the use of the first and second light signals.
Abstract: An optically based position location system, comprises multiple reflectorsositioned at known locations in an environment; a vehicle for traveling along a path in the environment; a first sensor for generating and detecting a collimated and polarized first light signal reflected from one of the reflectors, and for generating a first output signal in response to detecting the first light signal; a second sensor for generating and detecting a collimated and polarized second light signal reflected from the reflector reflecting the first light signal, and for generating a second output signal in response to detecting the second light signal; and a data processor which uses the first and second output signals for determining the distance between a reference coordinate on the vehicle and the reflector.

Journal ArticleDOI
TL;DR: The mechanical and dosimetric characteristics including dose linearity of this unit are presented and found to be suitable for SRS/SRT and the difficulty in absolute dose measurement for small cone is discussed.

Journal ArticleDOI
TL;DR: The extent of agreement between theory and experiment indicates that the physical mechanisms are understood and indirectly validates the theoretical models.
Abstract: Miniature light detectors with isotropic response (isotropic light dosimetry probes) permit quantitative measurement of light energy fluence rates in turbid media such as biological tissues. These isotropic probes are, for example, applied in photodynamic therapy to correlate light fluence in tissue with (tumour) tissue response, in vitro and in vivo. After description of its construction, two methods of calibration of an isotropic probe in air are discussed, in collimated and in diffuse light. The probe was first calibrated in air in collimated light, after which its response to diffuse light was checked in a flat and in a spherical geometry. Subsequently, the probe's response to collimated light in clear media, for example, water or glycerine which have refractive indices larger than that of air, has been established experimentally. The diffusion approximation to the transport equation in a simple spherical geometry has been used to calculate the probe's response as a function of the refractive index of clear media. The extent of agreement between theory and experiment indicates that the physical mechanisms are understood and indirectly validates the theoretical models.

Patent
02 Jul 1996
TL;DR: In this paper, the authors proposed a spatial light modulator with deformable mirror elements to obtain needed spectra while reducing the mechanical complexity of the spectrometer, and a controller that deforms the mirror elements according to a predetermined pattern.
Abstract: A spectrometer having a source of broad band infrared energy, a relay mirror that focuses the infrared energy at an intercepting mirror, a first object mirror that collimates the infrared energy from the intercepting mirror, a spatial light modulator that receives the collimated infrared energy and reflects it back to the first object mirror, the spatial light modulator including deformable mirror elements, and a controller that deforms the mirror elements according to a predetermined pattern. Deformable mirror elements obtain needed spectra while reducing the mechanical complexity of the spectrometer.

Journal ArticleDOI
17 Jun 1996
TL;DR: In this paper, a free-space system operating in the 75 GHz to 95 GHz range for measurement of the complex permittivity of matter is presented, where the complex transmission coefficient of a parallel polarized quasiplane wave through a planar sample is determined for different incidence angles.
Abstract: A free-space system operating in the 75 GHz to 95 GHz range for measurement of the complex permittivity of matter is presented. The complex transmission coefficient of a parallel polarized quasiplane wave through a planar sample is determined for different incidence angles. The quasiplane wave is realized by a collimated Gaussian beam. The complex permittivity is subsequently calculated from the measured data by applying a nonlinear least-squares method. Errors induced by multiple reflections between the transmitting and receiving horn antennas are removed by a time-domain gating technique. The design of the quasioptical measurement setup is based on Gaussian beam optics. A dielectric lens collimates the beam of the transmitting horn antenna for minimization of diffraction effects at the edges of the sample. In order to verify the Gaussian beam and thin lens approximations at millimeter wavelengths, the far-field pattern of the horn antenna and the dielectric lens system has been measured. The performance of the measurement setup has been tested using glass samples.

Patent
16 Oct 1996
TL;DR: In this article, a laser communication system adapted for use in a satellite communication system is described, which includes a plurality of active and passive optical elements packaged in a monolithic, or single block, structure for interfacing between a focusing beam director of the satellite and laser transmitters/receivers of the laser communications system.
Abstract: A laser communication system adapted for use in a satellite communication system. The satellite carries a laser communication system. The laser communication system includes a plurality of active and passive optical elements packaged in a monolithic, or single block, structure for interfacing between a focusing beam director of the satellite and laser transmitters/receivers of the laser communication system. Laser energy is directed between the beam director and the transmitters/receivers by the active and active optical elements, such laser energy passing through the monolithic structure solely as collimated light. In this way, relay elements, such as diffractive optics and focusing lenses, and there concomitant alignment requirements, are eliminated from the monolithic structure.

Patent
23 Jul 1996
TL;DR: In this paper, the shape of the jaw arrangement and the collimated beam of X radiation from the LINAC, can be changed and conformed in a very flexible and versatile way.
Abstract: This invention relates to a novel dynamic collimator which can be adapted to a linear accelerator (LINAC). The collimator is such that the shape of the jaw arrangement, and therefore the collimated beam of X radiation from the LINAC, can be changed and conformed in a very flexible and versatile way. In a preferred embodiment of the invention, the collimator has three pairs of opposing, parallel jaws, each pair of jaws being moveable, under control, to open and close in variable amounts. Each set of pairs may be oriented at a 60° orientation such that the open transmission area of the collimator has a hexagonal shape. Variations on this sixth jaw collimator, including larger numbers of jaws, also are included within the invention. The variety of shapes with such a variable hexagonal collimator is enormous. Irregular target volumes can be filled by beams of radiation that can be nested because of the hexagonal nature of the jaw configuration, giving it added conformal shaping capabilities. Variable angles of orientation between the jaw pairs are also included within the invention so that rectangular shapes may also be achieved.

Proceedings ArticleDOI
17 May 1996
TL;DR: In this article, the movement of polarized light through the superficial layers of the skin was visualized using a video camera with a polarizing filter, which indicated the attenuation of polarization as a function of distance between the source and point of photon escape from the phantom.
Abstract: The movement of polarized light through the superficial layers of the skin was visualized using a video camera with a polarizing filter. This study constitutes a description of the impulse response to a point source of incident collimated linearly polarized light. Polarization images reject unwanted diffusely backscattered light from deeper in the tissue and the specular reflectance from the air/tissue interface. Two experiments were conducted: (1) Video polarization reflectometry used a polarized HeNe laser (633 nm) pointing perpendicularly down onto a phantom medium (0.900-micrometer dia. polystyrene spheres in water). The video camera was oriented 10 degrees off the vertical axis and viewed the irradiation site where the laser beam met the phantom. Video images were acquired through a polarizing filter that was either parallel or perpendicular with the reference plane defined by the source, camera, and irradiation site on the phantom medium's surface. The source polarization was parallel to the reference plane. The two images (parallel and perpendicular) were used to calculate a polarization image which indicated the attenuation of polarization as a function of distance between the source and point of photon escape from the phantom. Results indicated a strong polarization pattern within approximately 0.35 cm (approximately 2.2 mfp') from source. [mfp' equals 1/(microna plus microns')]. (2) Optical fiber reflectometry using a polarized diode laser (792 nm) coupled to a polarization-maintaining single-mode fiber, and a multi-mode fiber collector to collect regardless of polarization. Reflectance as a function of fiber separation was measured for the source fiber oriented parallel and perpendicular with the reference plane. Results indicated that the strongest polarization propagated within approximately 0.43 cm (2.2 mfp') from source. The polarization survived approximately 2.2 mfp', which for skin at 630 - 800 nm (mfp' approximately equals 0.066 cm) corresponds to 1.5 mm (or 6.4 ps of travel at the speed of light). Using 6.4 ps as a maximum time of survival, classical paths of photon transport (Feynman paths) were calculated to illustrate the expected depth of interrogation by polarized imaging. The expected mean depth of photons is about 0.36 mm at these longer wavelengths. Shorter wavelengths would result in a shorter mfp' and therefore more superficial imaging of the skin. Polarization images offer an inexpensive approach toward 2-D acquisition of time- gated images based on the early light escaping the tissue. Polarization imaging is an opportunity for a new form of optical image especially useful for dermatology.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.