Showing papers on "Collimated light published in 1992"

Using light as a lens for submicron, neutral-atom lithography.

Abstract: We show that light can be used as a lens to focus a collimated neutral atomic beam to submicron dimensions during deposition onto a substrate. We have used an optical standing wave at 589 nm as an array of cylindrical lenses to focus a perpendicular sodium beam into a grating on a substrate, with a periodicity of 294.3\ifmmode\pm\else\textpm\fi{}0.3 nm. This result is the first direct evidence of submicron focusing of atoms by light, and represents a fundamentally new scheme for submicron lithography.

Modeling light reflection for computer color vision

Abstract: In computer vision applications, analysis of shading information requires a proper model of light reflection from object surfaces. To overcome the shortcoming of the most often used model and to extend the reflection model for computer color vision, an examination is made of the light reflection problem using the bidirectional spectral-reflectance distribution function (BSRDF) to specify both incident- and reflected-beam geometries. It is shown that the product form can still be retained for a polychromatic light source under two lighting conditions: the light source is collimated; or the spectral factor and the geometric factor can be separated for both the light source and the BSRDF of the surface. The reflection model is then applied to the formulation of a neutral-interface-reflection model, which is tested experimentally. The results show the adequacy of this type of model for surfaces of some material compositions, e.g. plastics, plant leaves, painted surfaces, orange peels, and some glossy cloth, but not for others, e.g. colored paper and some ceramics. >

Catadioptric reduction projection optical system

Abstract: In a cata-dioptric optical system having a combination of a reflection system and a refraction system for reduction-projecting an object on a first plane onto a second plane, a polarization beam splitter and a quarter wavelength plate are provided to split the incident light and the reflected light. The light beam directed to the polarization beam splitter is converted to a substantially collimated light beam by a first group of lenses. A second group of lenses are arranged between the polarization beam splitter and a concave reflection mirror to diverge the light beam. The light reflected by the concave reflection mirror is directed back to the polarization beam splitter with a substantially collimated state by the second group of lenses. The light beam from the second group of lenses transmitted through the polarization beam splitter is focused by a third group of lenses having a positive refraction power to form a reduced image.

Direct retinal scan display with planar imager

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

Portable laser device for alignment tasks

Abstract: A portable, battery powered, self-levelling alignment tool for simultaneously indicating level, plumb and square. A projection unit including a laser diode, a collimator, and an optical system is located in a projection unit which is pendulously suspended inside a housing. The optical system divides a collimated beam from the laser diode and the collimator into output beams having a generally perpendicular relationship with each other. The projection unit may be balanced such that at least one of the output beams is substantially level and other beams thus indicate plumb or square.

Method and apparatus for patterning an imaging member

Abstract: A device for patterning an imaging member (46) is provided. The device comprises a light source (24) which emits light rays (26). Light rays (26) pass through a collimator lens (28) to collimate the light rays (30). The light then strikes a spatial light modulator (32) which is controlled by a computer (40) to reflect the light (42). The light passes through an imaging lens (44) to magnify the pattern for striking imaging member (46). Imaging member (46) is thus patterned by changing modulator (32) by computer (40).

Application of the convolution method for calculation of output factors for therapy photon beams.

Abstract: The output factor for a therapy photon beam is defined as the dose per monitor unit relative to the dose per monitor unit in a reference field. Convolution models for photon dose calculations yield the dose in units normalized to the incident energy fluence with phantom scatter intrinsically modeled. Output factors calculated with the convolution method as the dose per unit energy fluence relative to the calculated dose per unit energy fluence in a reference field could deviate as much as 5% if corrections are not made for perturbations due to treatment head scatter. Significant perturbations are particles backscattered from the collimators to the monitor and photons forward scattered from the filter and collimators in the treatment head. The forward scatter adds an "unmonitored" contribution to the total energy fluence of the beam. A model is developed that describes the field size dependence of these perturbations for conversion of output factors, calculated with the convolution method, to machine output factors as an integrated part in treatment planning. The necessary machine characteristics are derived from measurements of the output in air for a limited set of field sizes. The method has been tested using five different multileaf collimated irregular fields at 6 MV and for a large set of rectangular fields at 5, 6, and 18 MV and found to predict output factors with an accuracy better than 1%.

Infrared image projector utilizing a deformable mirror device spatial light modulator

Abstract: The mirror elements mirror device spatial light modulator are selectively deflected. Such deflection causes incident infrared radiation to be reflected in selected directions. The number of deflected mirror elements as well as the degree of deflection determines the amount of reflected radiation which travels through an aperture and is collimated by suitable imaging optics, thus creating an infrared image that appears to be at infinity.

Collimated beam of light and systems and methods for implementation thereof

Abstract: A method and system for producing a collimated beam of light having a substantially uniform flux density across the entire beam includes a light source adapted to emit light rays; a light integrator adapted to collimate the light rays and provide a uniform flux intensity; and a pair of reflectors adapted to reflect all of the light from the light source into the light integrator. The light integrator includes a fly-eye arrangement of light pipes. Each light pipe includes a pair of lenses adapted to bend the light rays towards the normal to collimate the light rays. In addition the light pipes may be juxtaposed to produce a collimated light beam having a uniform flux density and a desired geometrical configuration (i.e. rectangular, circular).

Position and orientation measurement device

Abstract: A device for non-contacting measurement of the orientation in space of a movable measuring object, such as the end-effector of a robot, uses a retro-reflector having three mutually orthogonal reflecting surfaces. This retro-reflector is rigidly attached to the measuring object. Reference marks are provided on the retro-reflector. A laser emits a laser beam. A beam expander optical system in the path of the laser beam provides a collimated light beam of larger diameter than that of said laser beam. The light beam passes through a stationary section, where the path of rays of the light beam is stationary, to a beam directing device. The beam directing device directs collimated light beam onto the retro-reflector. The light beam is returned by the retro-reflector substantially into itself. The beam directing means has movable reflecting surfaces for tracking, with said light beam, the movable measuring object. A semi-transparent mirror is arranged in the stationary section of the returned light beam for deflecting part of this returned light beam to a plane where a picture with a pattern caused by the reference mark is formed. A picture detector is arranged in this plane, and detects the picture of the reference mark and provides corresponding picture information. A processor derives, from this picture information, output data representing the orientation in space of the retro-reflector and thereby the orientation in space of the measuring object.

Scanning rangefinder with range to frequency conversion

Abstract: An optical scanning rangefinder has been developed that creates a depth map of its surroundings by scanning a beam of modulated, collimated light and observing reflections from proximate surfaces. The scanning system uses dual rotating prisms to deflect the transmitted beam and collect a portion of the reflected light, which is focused on a photodetector and converted to an electrical signal. This signal is amplified, AC coupled, and inverted. The inverted signal drives the modulator for the light source. When sufficient light is received by the detector, this sytem forms an oscillator, the frequency of which depends on the distance to the illuminated surface. This frequency can easily be measured to a high degree of accuracy, and the distance to the surface derived from it. The scanner achieves a field of view of 360 degrees horizontally by 52 degrees vertically.

Electron beam characteristics of the 50-MeV racetrack microtron.

Abstract: Electron beams in the MM50 racetrack microtron are generated by computer controlled scanning of a well-focused electron pencil beam. The treatment head is optimized to give a minimum of scatter between the source position and the collimator plane by a general minimization of all scattering material in the beam and by replacement of the air in the treatment head by helium, which has a much lower linear scattering power than air. A double-focused multileaf collimator with a 31-cm collimator to patient distance is used both for electron and photon collimation. In general, no extra electron collimation is needed for the standard SSD of 100 cm. To make irregular field collimation at a distance this far from the patient possible, a number of requirements have to be fulfilled regarding the virtual source position and the spatial and angular distribution of the initial electron beam. The virtual source position has been found to be at a fixed position for different irradiation parameters. This is important for the use of the light field in electron beam treatment but also for achieving a high degree of accuracy in the dosimetry. Scatter from the multileaf collimator has not been found to give any significant contribution to the radiation field or to the monitor output factor of the MM50. Experimental dose distribution data on the MM50 have been compared to data both from other types of treatment units and to Monte Carlo simulations.

Fiber optic lighting system using conventional headlamp structures

Abstract: A lighting system particularly suited for an automotive application in which it is desired to utilize a central light source and couple the light output therefrom to a headlamp assembly having a number of conventional components includes introducing an output end of a light guide to the reflector assembly in place of an incandescent lamp, and disposing a mirror at the output end of the light guide to reflect light onto a conventional parabolic reflector. The mirror is preferably planar and serves to direct the light from the output end of the light guide to the parabolic reflector for collimation thereby and subsequent passage through a conventional lens member.

Laser surgical probe

Abstract: A laser surgical apparatus is disclosed in which laser energy can be directed at an angle relative to the longitudinal axis of the probe. The probe includes a reflecting surface directing the laser energy. The reflecting surface is transparent to visible light. In a preferred embodiment, the reflecting surface is on a rod cut at an angle to form a wedge, and a collimator is used to collimate the light beam before it reaches the reflecting surface.

Scanning microscope and scanning mechanism

Abstract: A scanning microscope comprises a sample supporting member on which a sample is supported, a light source which produces a light beam, a light projecting optical device with which an image of the light beam is formed as a small beam spot on the sample, and a light receiving optical device with which the light radiated out of the sample is condensed and an image of the condensed light is formed as a point image. A photodetector detects the point image. A movable member supports at least part of the light projecting optical device and at least part of the light receiving optical device together. The movable member is reciprocally moved such that the beam spot may scan the sample in a one-dimensional scanning direction. The light source is located on the side outward from the movable member. The light projecting optical device is provided with a collimating optical device for collimating the light beam, which has been produced by the light source, on the side outward from the movable member and guiding the collimated light beam to a direction parallel to the scanning direction, and a mirror, which is secured to the movable member and which reflects the collimated light beam towards the sample supporting member.

Night vision goggle compatible liquid crystal display device

Abstract: A full color, night vision goggle compatible, liquid crystal display device achieves uniform illumination and color integrity at wide viewing angles by creating collimated, uniform light in a backlight assembly before the light reaches an IR filter having a sharp cutoff between near IR and red, and thereafter diffusing the light which is emitted from the filter to create the desired wide viewing angle.

Apparatus and method for measuring the thickness of thin films

Abstract: An electro-optical imaging system for efficiently determining a thin film layer thickness of, for example, a wafer over a full aperture. Non-uniformities in this layer thickness are obtained by measuring the reflectance characteristics for a full aperture of a wafer surface and comparing this measured reflectance data to reference reflectance data by using numerical iteration or by using a calibration wafer having known layer thicknesses. To efficiently measure the reflectance characteristics of a wafer layer, a filtered white light source is used to produce a sequence of collimated monochromatic light beams at several different wavelengths. These collimated monochromatic beams are individually projected onto the entire surface of the wafer, and coherent interactions occur between this light as it is reflected from the physical boundaries in the wafer structure. As a result of these interactions an interference fringe pattern is formed on the surface of the wafer for each projected beam and, consequently, for each wavelength. A reflected image of each fringe pattern is projected onto a detector array of, for example, a charge coupled device (CCD) camera, where the full aperture of this image is then captured. The fringe pattern image is captured by digitizing pixels in the CCD camera detector array corresponding to the image present. A reflectance map of the entire wafer surface is generated from this captured fringe pattern image. Several reflectance maps are generated from each measured wafer to eliminate thickness ambiguities which may result from outer layers having phase thicknesses greater than 2π.

Projection television display utilizing Bragg diffraction cell for producing horizontal scan

Abstract: Apparatus for horizontally scanning an image corresponding to electronic video input information utilizing a Bragg Diffraction cell in which collimated light from a laser directed through the cell is modulated by a real-time fourier transform of a line of video input information, thereby to produce a one line acoustic hologram in the cell which is reconstructed at a infinity as a stationary image corresponding to the horizontal line of video information. Using a suitable lens system, the stationary image is re-imaged at a plane positioned at a fixed distance from the Bragg Diffraction cell. The scanner is useful in image projection systems, in which the horizontal line image is vertically scanned by a galvanometer driven mirror vibrating in synchronism with the vertical blanking interval of the input video.

Monte Carlo modelling of the performance of a rotating slit-collimator for improved planar gamma-camera imaging

Abstract: Planar imaging with a gamma camera is currently limited by the performance of the collimator Spatial resolution and sensitivity trade off against each other; it is not possible with conventional parallel-hole collimation to have high geometric sensitivity and at the same time excellent spatial resolution unless field-of-view is sacrificed by using fan- or cone-beam collimators We propose a rotating slit-collimator which collects one-dimensional projections from which the planar image may be reconstructed by the theory of computed tomography The performance of such a collimator is modelled by Monte Carlo methods and images are reconstructed by a convolution and backprojection technique The performance is compared with that of a conventional parallel-hole collimator and it is shown that higher spatial resolution with increased sensitivity is possible with the slit-collimator For a point source a spatial resolution of some 6 mm at a distance of 100 mm from the collimator with a x7 sensitivity compared with a parallel-hole collimator was achieved Applications to bone scintigraphy are modelled and an improved performance in hot-spot imaging is demonstrated The expected performance in cold-spot imaging is analytically investigated The slit-collimator is not expected to improve cold-spot imaging Practical design considerations are discussed

Design of a pulsed X-ray system for fluorescent lifetime measurements with a timing accuracy of 109 ps

Abstract: The design of a table-top pulsed X-ray system for measuring fluorescent lifetime and wavelength spectra of samples in both crystal and powdered form is described. The novel element of the system is a light-excited X-ray tube with a tungsten anode at+30 kV potential. The S-20 photocathode is excited by a laser diode with a maximum rate of 10 MHz, each pulse having 10/sup 7/ photons. In a collimated 2 mm*2 mm beam spot 40 mm from the anode, >1 X-ray per pulse is expected. A sample is exposed to these X-rays and fluorescent photons are detected by a microchannel PMT (photomultiplier tube) with a photoelectron transit time spread of 60 ps FWHM, a sapphire window, and a bialkali photocathode (wavelength range 180-600 nm). The combined time spread of the laser diode, the X-ray tube, and a microchannel tube has been measured to be 109 ps FWHM. To measure wavelength spectra, a reflection grating monochromator is placed between the sample and the PMT. >

Laser diode liquid-level/distance measurement

Abstract: A laser diode distance measurement device includes a laser diode assembly 10, comprising a laser diode and photodiode, which emits light 17 to a lens 19 which provides collimated light 20 incident on a float 22 which is covered with reflective tape on its top surface 24 The light 20 is reflected from the float 22 back to the laser diode assembly 10 which causes the assembly 10 to provide a signal having magnitude pulses (due to coherent interference) on a line 15 to a liquid level measurement circuit 14 related to the distance L to the float 22 Use of the collimated beam 20 and reflective tape on the float 22 minimizes speckle while providing adequate optical intensity feedback The laser assembly 10 is driven by a sawtooth waveform signal that reduces electronic processing The distance measurement circuit 14 blanks-out the feedback signal during discontinuities of the laser diode drive signal to minimize associated noise from distorting the distance measurement Alternatively, the float may be omitted and the tube 11 made small enough to provide a meniscus effect curvature at a liquid surface 250 which provides a curved reflective surface to reflect the incident light 20, in a consistent fashion, back to the laser assembly 10

High resolution compact optical sensor for scanning three-dimensional shapes

Abstract: An optical sensor for three dimensional shapes includes a laser that produces a lamellar plane beam which illuminates the surface of an object. The lamellar plane beam produces a curvilinear luminous trace that is scanned by at least one video camera, to produce information that is then converted into digital data representing pixel coordinates. The sensor includes a lightbox having a common housing that is positioned a short distance above the object to be scanned. The lightbox housing also includes a laser source that produces a collimated rectilinear beam and an optical device for converting the rectilinear beam into the lamellar plane beam. The lightbox housing also includes a device for lengthening the optical path of the lamellar plane beam, comprising two fixed plane mirrors in face to face relationship to produce a plurality of reflections between a beam entry point and a beam exit point of the lightbox. The small physical distance between the housing and the object is compensated by a virtual optical distance so that there is a correlative increase in the depth of field of the usable region of the lamellar plane beam at the beam exit point from the housing.

Collimated display having wide horizontal and vertical fields, in particular for simulators

Abstract: The display of the invention includes two identical image-forming devices (1, 2), each including a spherical mirror (3, 7), a spherical screen (4, 8) and a projector (5, 9) These two devices are superimposed and centred on a vertical axis (10) passing through the eye of the observer One (1) covers the lower part of the vertical field and the other (2) the upper part The vertical field may be at least 90 DEG

Error analysis of surface normals determined by radiometry

Abstract: Surface normals can be computed from three images of a workpiece taken under three distinct lighting conditions without requiring surface continuity. Radiometric methods are susceptible to systematic errors such as: errors in the measurement of light source orientations; mismatched light source irradiance; detector nonlinearity; the presence of specular reflection or shadows; the spatial and spectral distribution of incident light; surface size, material, and microstructure; and the length and properties of the light source to target path. Typically, a 1° error in surface orientation of a Lambertian workpiece is caused by a 1 percent change in image intensity due to variations in incident light intensity or a 1° change in orientation of a collimated light source. Tests on a white nylon sphere indicate that by using modest error prevention and calibration schemes, surface angles off the camera axis can be computed within 5°, except at edge pixels. Equations for the sensitivity of surface normals to major error sources have been derived. Results of surface normal estimation and edge extraction experiments on various non-Lambertian and textured workpieces are also presented.

A simple intrinsic optical-fibre chemical sensor

Abstract: This paper describes an intrinsic optical-fibre sensor for the measurement of variations of the refractive index of a medium acting as the cladding. A multimode fibre is illuminated with a laser beam incident at an oblique angle so that some of the rays trapped in the core are refracted if the index of the cladding is slightly shifted. Owing to the stability of the light source, a variation of about 2 × 10 −5 in the refractive index is readily detectable. The sensitivity and the linearity of the sensor depend on the angle of incidence of the collimated beam. This set-up can be used for the remote analysis of liquid or polymeric mixtures. The realization of a gas sensor is also presented: the bare core of the fibre is coated with a polymeric film whose refractive index varies during gas absorption. An example of methane detection at concentrations less than the lower explosive limit with a polyoxyethylene film is given. This simple and low-cost sensor can be used for detection of other gases after the preparation of specific sensitive claddings.

Low aberration diffraction grating system

Abstract: A light analysis system is disclosed and comprises a source of substantially collimated light to be analyzed The source comprises a sample excited by a collimated laser light source, and further comprises a holographic notch filter having the characteristic of reflecting light at the excitation wavelenghth at which the source is excited An aberration corrected concave focusing diffraction grating receives the collimated light and focuses it at a point corresponding to its wavelength A detector detects light at a desired wavelength focused by the diffraction grating The holographic notch filter is positioned to filter the source of substantially collimated light to be filtered and the holographic notch filter is oriented substantially at an angle with respect to the collimated laser light source to result in a path length for the collimated laser light source which constrains a path length through the notch filter which causes the collimated laser light to be reflected by the filter away from the grating The grating is an aberration corrected concave focusing diffraction grating The collimated light is in the form of a bundle having a width on the order of ten millimeters

Line-of-light illuminating device

Abstract: A line-of-light illuminating device includes an optical lightpipe for receiving and transmitting light by internal reflection and an integral optical lens located at an emission portion of the lightpipe for focusing the reflected light into a collimated line-of-light beam. The lightpipe and lens are preferably injection molded in a single shot as a unitary device. The lightpipe preferably has an isosceles triangular cross-sectional shape with an apex formed at the point where the two equilateral sides join. A reflective surface is formed along the apex on the emission portion of the lightpipe, and the lens is located on the side opposite the apex. The internally reflected light striking the reflective surface is reflected perpendicularly therefrom to the lens. The lens focusses the reflected light into the collimated line-of-light beam.

Apparatus and method for inspecting a test lens, method of making a test lens

Abstract: An apparatus for inspecting a test lens, such as an intraocular lens, comprising a light source and collimating lens positioned to receive light from the light source and direct collimated light to the test lens. A plurality of targets are positionable at the object focal plane of the collimating lens so that there is an image of the target at the image focal space of the test lens. The image of the target has generally radially extending and alternating first and second sectors with each of the first sectors being relatively light and each of the second sectors being relatively dark. Modulation transfer function is determined by determining the image contrast along a combination of selected ring-shaped regions of the image.

A method of calculating peripheral dose distributions of photon beams below 10 MV.

Abstract: The radiationdose outside the radiotherapytreatment field can be of clinical concern and, therefore, a method of accurately predicting the peripheral doses received by tissues would be beneficial. This paper describes a semiempirical method developed for calculating the peripheral dose received at points outside the collimated field edge for incident photon beams with energies below neutron production thresholds (<10 MV). The dependence of the peripheral dose upon depth, distance, field shape and size, azimuthal angle about the central axis, external contour variations, and tissue heterogeneities are accounted for by this calculation. Predictions by this algorithm are compared with measurements and it is shown that the method is capable of reproducing the measured peripheral dose values usually to within the statistical uncertainties of the data.