Showing papers on "Collimated light published in 1993"

A scanning line source for simultaneous emission and transmission measurements in SPECT.

Abstract: A scanning collimated line source for simultaneously acquiring emission and transmission data from a gamma camera has been developed. The line source is microprocessor-controlled and incorporates hardware to electronically window the spatial gamma camera signals in order to separate the emission signals of the subject from transmission signals from the line source. The device improves upon the previously described emission-transmission scanning technique using a flood source in three ways: (1) it overcomes the limitation that the transmission radionuclide must have a lower energy than the emission radionuclide; (2) it provides narrow-beam (scatter free) attenuation measurements of the subject being examined; and (3) it reduces the radiation exposure to staff. Attenuation coefficients for an elliptocal water-filled phantom were measured to be mu = 0.15 +/- 0.01 cm-1. The technique has been validated in phantom and human studies using a range of radionuclide combinations and imaging geometries and gives equivalent results using separate and simultaneous acquisitions.

Backlight assembly for improved illumination employing tapered optical elements

Abstract: An improved backlight assembly comprising an array of apertures in close proximity to a light source, an array of tapered optical elements that have a light input surface area smaller than the light output surface area. Light rays pass through the apertures and are directed to the optical elements which transmit the light rays via internal reflection to provide a partially collimated light source. The light rays then pass through an array of microlenses that transmit the light rays via refraction and provide a substantially more collimated light source for the display elements of a display. The backlight assembly is advantageously used as a backlighting means for electro-optical displays, especially those designed for military and avionics applications.

Frequency converted laser diode and lens system therefor

Abstract: A compact semiconductor laser light source providing short wavelength (ultraviolet, blue or green) coherent light by means of frequency doubling of red or infrared light from a high power diode heterostructure. The high power diode heterostructure is a MOPA device having a single mode laser oscillator followed by a multimode, preferably flared, optical power amplifier. A tunable configuration having an external rear reflector grating could also be used. A lens could be integrated with the MOPA to laterally collimate the light before it is emitted. Straight or curved, surface emitting gratings could also be incorporated. An astigmatism-correcting lens system having at least one cylindrical lens surface is disposed in the path of the output from the MOPA to provide a beam with substantially equal lateral and transverse beam width dimensions and beam divergence angles. A nonlinear optical crystal or waveguide is placed in the path of the astigmatism-free symmetrized beam to double the frequency of the light. Single pass or multipass configurations with reflectors could be used, as well as external resonator and segmented, periodically poled waveguide configurations.

Fast Transmission CT for Determining Attenuation Maps Using a Collimated Line Source, Rotatable Air-Copper-Lead Attenuators and Fan-Beam Collimation

Abstract: We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation.

Optical collimating device employing cholesteric liquid crystal and a non-transmissive reflector

Abstract: An optical collimating device employs an optical (concave) mirror and cholesteric liquid crystal element to collimate and project image light into the line-of-sight of an observer in efficient manner. Image light is generated with light components within a predetermined bandwidth and with a predetermined rotary sense. The image light is directed so that it is reflected by the concave mirror, expanding (collimating) the image light, projecting in onto a cholesteric liquid crystal element that reflects those components of the image light within the bandwidth B and having the proper rotary sense of circular polarization. The cholesteric liquid crystal element substantially reflects the returned image to the observer.

X-ray flux enhancement in thin-film waveguides using resonant beam couplers.

Abstract: We present experimental evidence for achieving significant x-ray flux enhancement by coupling a highly collimated and monochromatic synchrotron x-ray beam into a Si/polyimide/SiO 2 thin-film waveguide. The observed 20-fold flux increase agrees with theoretical predictions and was limited only by absorption of the 1 A x rays in the waveguide structure

Optical device with two lens arrays with the second array pitch an integral multiple of the first array pitch

Abstract: A three-dimensional display comprises a spatial light modulator (13), such as a liquid crystal display, sandwiched between first and second lenticular screens (12, 16). The pitch of the lenticules of the second screen (16) is an integral multiple of that of the first screen (12). The spatial light modulator (13) comprises a plurality of cells aligned with the lenticules of the first screen (12). A linear array of sequentially illuminated light sources (1-8) is focused by an optical system (10) into a plurality of collimated light beams with different angles of incidence on the first screen (12). For each illumination of the light sources, the spatial light modulator carries a plurality of 2D interlaced views.

A backlighting assembly utilizing microprisms and especially suitable for use with a liquid crystal display

Abstract: An assembly (10) for backlighting a liquid crystal display (12) is disclosed herein along with the liquid crystal display (12) itself and a specific light polarization arrangement. The assembly for backlighting the liquid crystal display (12) includes a backlighting light pipe (14) into which light is directed in a particular manner and a specifically configured arrangement of immediately adjacent microprisms which cooperate with the backlighting light pipe (14) for reflecting light within the ladder upwards through one of its surfaces (32) in a generally collimated manner. The liquid crystal display backlighting assembly (10) is also disclosed including a specifically designed arrangement for collimating the light into the light pipe (14) such that the light exiting the light pipe does so on a more collimated manner.

Projection display system including a collimating tapered waveguide or lens with the normal to optical axis angle increasing toward the lens center

Abstract: The present invention provides a lighting device including a light source; a reflecting mirror for reflecting light emitted by the light source in a determined direction; and a compensating element for receiving the light from the reflecting mirror and allowing the light to outgo in the form of parallel rays. Further, a projection type image display system including the above-mentioned lighting device and a display element for forming an image by receiving light from the lighting device is provided. According to the present invention, light can be emitted with a satisfactory degree of parallelization and an even illuminance, constant irregularity due to the photoelasticity can be degraded, and the degradation in brightness of a projected image due to a low ratio of aperture can be avoided. Thus, a uniform image with no illuminance irregularity can be projected.

Electro-optic flashlight electro-optically controlling the emitted light

Abstract: A flashlight is disclosed comprising a light source and a reflector for collimating the light emitted by the light source to form a collimated light beam. An electro-optically controlled region is disposed forwardly of the light source, the collimated light beam being incident upon and passing through the electro-optic region. The electro-optic region may be operated in at least two states. In a first embodiment, and in a first state, the electro-optic region does not substantially affect the collimation of the light beam incident thereon, and the flashlight produces a spot beam. Also in the first embodiment, and in a second state, the electro-optic region scatters forwardly the collimated beam incident thereon, and thus the flashlight produces a well-diffused flood beam.

Helmet-mounted optical systems

Abstract: An optical system mounted on a helmet (29) for superimposing a collimated image of a display object on the external view of the helmet's wearer comprising: display object means (1a, 1b) mounted on the helmet for generating a display; a concave collimator (6a, 6b) for collimating light from said display; an optical relay unit (3a, 3b) located in the forehead region for generating an intermediate image of said display in the focal plane of the collimator; a reflecting surface (4a, 4b) for reflecting display light from the relay unit towards the collimator; and an inclined combiner (5) essentially transparent to incoming display light and to the wearer's external view, for reflecting display light reflected from the collimator towards the viewer's eye.

Tumor tissue characterization apparatus and method

Abstract: An instrument for characterizing tumor tissue includes a broad-band light source, a monochromator for filtering collimated light from the broad-band light source, a scanner for scanning the monochromator through a range of predetermined wavelengths, and a hollow needle including a shaft with a tip on one end and a base on the other end. An optical fiber is positioned within the hollow needle for delivering light from the monochromator through the tip to a desired tissue region, A photodiode is mounted in the shaft and has a light sensitive surface facing outward from the shaft for detecting back-scattered light from the tissue region. The back-scattered light detected by the photodiode is monitored by a computer which records the optical absorption spectrum of light back-scattered from the tissue region at discrete locations in the tissue as the needle is inserted or withdrawn through the mammographically abnormal tissue.

Backlit liquid crystal display with integral collimating, refracting, and reflecting means which refracts and collimates light from a first light source and reflects light from a second light source

Abstract: An improved NVG compatible day/night backlighting assembly for a color liquid crystal display includes a daytime high intensity light source, an edge-mounted nighttime low intensity light source, and an integral collimating/reflecting/image splitting lens which collimates and image splits the light emitted from the high intensity daytime light source, and reflects upward the low intensity light rays emanating from the low intensity edge-mounted light source.

Apparatus and method for the analysis of particle characteristics using monotonically scattered light

Abstract: An apparatus for the analysis of individual particle characteristics from an aerosol or other suspension of particles, of the type having a scattering chamber (15) with an ellipsoidal reflector (17) and an orifice leading to a rear chamber (20), and a monochromatic light source (10) adapted to transmit a collimated beam of light (11) along the main axis of the reflector (17) to impinge on a stream of the particles reflector (17), has an optical system (17, 32, 33, 34) arranged to collect light back-scattered from a particle, through a solid angle of at least 3π, pass the light to a a ccd video recorder (36) having a two dimensional array of a multitude of sensors. The recorder (36) is associated with a data processor (37) and with an imaging screen (35) positioned such that rays of light scattered from the particle and imaged thereon by the optical system (17, 32, 33, 34) are monotonically ordered with respect to the angle of scattering of the rays from the particle.

Photon beam characteristics on the MM50 racetrack microtron and a new approach for beam quality determination

Abstract: The photon beams of the MM50 racetrack microtron have special characteristics which make them more suitable than conventional photon beams for precision radiation therapy with good dosimetric control. The beam flattening is obtained by the scanning of an elementary beam instead of using a flattening filter. This will give a number of advantages such as the possibility to optimize field flattening to individual field forms and field sizes. The radiation quality is the same across the whole beam, which gives smaller changes in dose profiles with depth and also makes it easier to perform careful dose planning. Beam collimation is mainly performed by a multileaf collimator and the special design of the treatment head gives nearly ideal characteristics for dose determination in an arbitrary point in the treatment fields. The output factor has been shown to depend almost solely on scattering within the treatment field. The conventional methods for beam quality characterization have been found less suitable at high energies and a new method based on HVL measurements in water is proposed.

Illuminator for use with a remote light source

Abstract: An illuminator for vehicle exterior lamps using a remote light source. Light is transmitted to the illuminator by a light guide, such as a fiber optic light pipe. The illuminator utilizes a complex mirror and a reflector to collect and collimate over 80% of the light from remote light source into a desired parallel beam for use as an automotive headlight.

Compact optical head

Abstract: A compact optical head for reading or writing data on an optical disc is disclosed wherein the optical head comprises an integrated laser diode/photodetector package, a half-cube beamsplitter, and an objective lens. Light emitted from a diode laser is in transmitted to the beamsplitter and deflected towards the objective lens. The objective lens focuses the incident light on a focal point on the surface of the disc. A reflected beam travels along the same path as the incident light and is deflected by the beamsplitter toward a photodetector contained in the integrated package, wherein the photodetector is displaced from the laser diode. Other embodiments of the beamsplitter are disclosed which include a wedged plate for transmitting collimated light emitted from the laser diode, and a cylindrical lens for introducing astigmatism into the reflected beam. The present invention provides a substantial reduction in the size and volume required by the optical head, advantageously allowing the head to be easily integrated with an actuator for focussing and tracking the incident beam on the disc.

Combination light concentrating and collimating device and light fixture and display screen employing the same

Abstract: The present invention is directed toward a light concentration and collimation device including a tapered body concentrator and a curved, preferably parabolic, reflective collimator combined in a unit such that the apex of the tapered body extends into the reflective collimator through its apex. The concentrator is preferably hollow with a reflective inner surface to funnel light from the base to the apex where an aperture allows the concentrated light to enter the collimator proximate to its focus. The light is then reflected from the inner surface of the collimator to form a beam of collimated light. The concentration and collimation device is particularly useful in visual display apparatus and may be combined with a spectral peak light source and a spectral distributor to produce individual collimated beams of light at specific wavelengths.

Direct retinal scan display

Abstract: A display which writes an image directly on the retina of an eye. The display includes a laser (20) which produces a collimated light beam that is modulated (22) with video information and is then scanned (24) and directed through the eye pupil (28) to produce an image on the retina. The scanning uses micro-machined mirrors, electro-optic or acousto-optic devices (32, 34) which are extremely small and require very low power.

Design of gradient-index lens systems for laser beam reshaping

Abstract: Refractive systems using two gradient-index lenses have been designed to convert a collimated Gaussian-profile laser beam into a plane wave with a uniform intensity distribution. The axial gradient-index distribution for two lenses is determined by using the energy conservation condition and the constant optical path-length condition. The design consideration and theoretical analysis are presented along with several applications.

Diode laser having minimal beam diameter and optics

Abstract: A diode laser and optical system uses the minimum number of elements to obtain a small diameter beam (1 mm). A large numerical aperture lens collimates the full energy from the diode and the oval shaped output of the collimator is corrected for astigmatism by means of a cylinder lens and made circular by two identical prisms arranged to receive the corrected, collimated beam directly at a right angle surface of the first prism and transmit the beam after deflection to the second prism further which demagnifies the beam producing the round (≦1 mm diameter) beam spot output of the laser. The output beam is well collimated (1 mRad) and wave front aberration is diffraction limited. The spot size at 50 feet distance is maintained. In order to hold total Gaussian distribution energy, the prisms are coated with a multilayer dielectric thin film eliminate reflection and to transmit the TE mode wave without loss at the Brewster angle.

Reflective grain defect scanning

Abstract: Grain structure defect scanning is accomplished by a pair of light detectors directed toward an inspection point illuminated by a collimated light beam incident upon the inspection surface at a given angle of incidence. One detector, the specular detector, is positioned generally along the specular angle of reflection as defined by the angle of incidence and the other detector, the diffuse detector, lies substantially along the angle of incidence. When specular reflection dominates, as when the inspection point corresponds to clearwood, the specular detector indicates a higher reflective light intensity than the diffuse detector. When diffuse reflection dominates, however, as when the inspection point corresponds to a grain defect, both detectors indicate similar reflective light intensity. Grain defect discrimination is accomplished by calculating a ratio of specular detector output to diffuse detector output. Further analysis of the relative magnitudes of the detector outputs provides a basis for identifying grading marks, such as ink and wax marks, at the inspection point.

High spatial resolution imaging spectrograph

Abstract: A high resolution fast imaging spectrograph is disclosed which provides 400 spatial channels and 100 spectral channels of information. A collimating mirror (10) and a focusing mirror (12) face a plane diffraction grating (14), which is positioned at an acute angle to the perpendicular to the optic axis. An elongated slot (16) is cut through approximately the center of the grating allowing the light source (18) to pass through the slot and onto the collimating mirror. A turning mirror (20), which is placed at the focus of the focusing mirror and adjacent to the slot, directs radiation to a camera mirror (22), which focuses a final image outside the instrument enclosure onto a detector (24). The light source to the instrument is provided by an optical fiber ribbon. The detector will commonly be a CCD or CID 2-D detector, permitting the simultaneous measurement of spectral distribution of a spatial profile. The instrument requires no power input, has no moving parts, and is completely passive with no operating controls or adjustments. Also disclosed is a commercially significant means to utilize the high spatial resolution imaging spectrograph in earth science remote imaging applications through the utilization of a reflecting telescope connected to the spectrograph by means of an optical fiber ribbon.

Coherent detection imaging for medical laser tomography

Abstract: Optical spectroscopy techniques are providing essential ways to characterize physical and chemical properties in living tissues and cells and then to monitor their functional changes occurring inside them. Thus they offer exciting possibilities for developing spectroscopic computed tomography in the optical region, especially in the red and near infrared regions, to acquire functional/physiological information through their unique and valuable reconstructed images. Nevertheless, its development and application in living tissues and systems are complicated and prevented practically by the diffuse nature of the image quality due to strong multiple scattering of light. In the present paper, we will review and discuss our recent studies on Coherent Detection Imaging (CDI) method which could provide at present one of the most reliable and feasible schemes for achieving the optical/spectroscopic computed tomography using various kinds of lasers for biomedical applications. This method is basically realized with the optical heterodyne detection technique, possessing both the properties of a highly directional antenna and an ultraA¢â‚¬â€sensitive receiver, and the image reconstruction based on the projection slice theorem from sets of line integrals of laser absorption along a large number of rays crossing the object with the parallel beam geometry. It is also postulated that the three fundamental conditions should be satisfied in principle in order to establish the optical absorption computed tomography on the basis of the conventional projection slice theorem. We have demonstrated experimentally the fulA¢â‚¬â€ fillment of these fundamental conditions using several biological tissues as well as scattering and diffusive samples by virtue of the optical heterodyne detection technique. Hence the applicability of the CDI method was confirmed in highly scattering and turbid media such as living tissues and bodies in which an object is completely obA¢â‚¬â€ scured from normal visual observation and from conventional direct detection techA¢â‚¬â€ niques. In consequence, we have achieved experimentally the twoA¢â‚¬â€dimensional direct (projection) imaging with some test objects immersed in biological tissues and the reconstructive tomographic imaging with various in vitro and in vivo objects such as chicken leg, chicken egg and human tumor specimens together with some plants and newA¢â‚¬â€born mouse head. The collimated optical beam from a cw laser operated usually less than 10 mW of the output power, selected suitably from a set of Ar, HeA¢â‚¬â€Ne, Kr, Ti:A1203 and Nd:YAG lasers in our CDI system, enabled us to display these images with the spatial resolution as good as approximately 200 tim to 700 tun in this experiA¢â‚¬â€ ment. Several typical results of these measurements are also shown and discussed in this paper.

X-ray diffraction apparatus

Abstract: An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

X-ray focusing using cylindrical-channel capillary arrays. I: Theory

Abstract: A detailed analysis of the focusing and collimation of x rays by circular-pore microchannel plates (MCP’s), or arrays of cylindrical capillaries, is presented. The focusing effect derives from external reflection of grazing-incidence rays at the interior surfaces of the hollow channels of the MCP and is similar to optical focusing by a spherical mirror. We give the point spread function of an MCP, taking into account surface roughness and misaligned channels. The calculation is based on multiply reflected rays and skew rays and is valid for a spherically curved MCP of any thickness. For comparison with experimental results the effects of a finite source and a detector aperture are also evaluated. This theory is compared with experiment.

Three dimensional mapping systems and methods

Abstract: A system for three dimensional mapping of a submarine surface includes (a) a light source for projecting a beam of collimated light that is reflective from the submarine surface including a laser of confined cross-sectional area, (b) a scanning unit to intercept the beam and project it in a first direction onto a selected area of the surface as a raster of pixels each at controlled X and Y coordinates of said surface and produce a reflection of the raster in a second direction, (c) a scanner processor to control the X and Y coordinates, (d) a compound lens capable of intercepting the raster reflection and focusing it as a scan image on a reception plane offset spatially from the scanning unit, (e) a position sensitive detector having a planosurface positioned substantially on the reception plane to sense the scan image and convert each pixel of the reflected raster into a pair of differential currents corresponding to the X and Y coordinates of the each pixel at said reception plane, (f) a signal processor to calculate from the differential currents range value voltages for the pixels, and (g) graphic display unit to convert the range value voltages into a visual representation of the scanned surface.

Fan-beam reconstruction algorithm for a spatially varying focal length collimator

Abstract: Fan-beam collimators are used in single-photon-emission computed tomography (SPECT) to improve the sensitivity for imaging of small organs. The disadvantage of fan-beam collimation is the truncation of projection data surrounding the organ of interest or, in those cases of imaging large patients, of the organ itself, producing reconstruction artifacts. A spatially varying focal length fan-beam collimator has been proposed to eliminate the truncation problem and to maintain good sensitivity for the organ of interest. The collimator is constructed so that the shortest focal lengths are located at the center of the collimator and the longest focal length is located at the periphery. The focal length is assumed to increase monotonically toward the edge of the collimator. A reconstruction algorithm for this type of fan-beam collimation, expressed as an infinite series of convolutions followed by one backprojection, is presented. Simulations show that only a small number of N terms in the series is needed to obtain high-quality reconstructions. Computer simulations showed that if the focal length function is smooth, the reconstructions are free of artifacts. >

Optical fiber sensor

Abstract: PURPOSE:To detect an object to be detected over a wide range by expanding beams and to stably detect the object with uniform light intensity by providing the optical fiber sensor with a lens for collimating the light emitted from an optical fiber to collimated beams of light and a reflection member having many reflection surfaces for reflecting these collimated beams of light. CONSTITUTION:A convex lens 21 and the reflection member 31 are disposed on the optical axis 4 of the optical fiber 11 on a light projection side and the reflection surfaces 31a of the reflection member 31 are formed into a saw tooth shape. The respective surfaces on the side of the respective saw tooth-shaped reflection surfaces 31a facing the convex lens 21 are formed to have angle of 45 deg. to the optical axis 4 and the light beams made incident as the collimated beams of light on the respective reflection surfaces 31a by the convex lens 21 are reflected in a direction perpendicular to the optical axis 4. Plural pieces of the beams opened in spacings are formed by the reflection surfaces 31a of the reflection member 31 facing the convex lens 21 and the apparent beam diameter is expanded. Consequently, the range for detecting the object to be detected is widened in one direction without increasing the size of the convex lens 21.