Showing papers on "Collimated light published in 1982"

Light scattering and absorption as methods of studying cell population parameters

Abstract: When a collimated beam of light encounters a system of biological cells or structures, part of the light may be absorbed, part is scattered, and the rest is transmitted. Transmitted and scattered light are measured to obtain information about the cells. Optical methods are among the most powerful tools for remotely and unobtrusively obtaining information about a sample suspension. Absorp­ tion measurements routinely provide information about compounds within the cells. The experimental data is interpreted in terms of empiri­ cal spectra of solutions of the compounds involved. Scattered light is a source of information about the morphological properties of cells and large subcellular structures: size, shape, state of aggregation, etc. EffeCts of scattering have similarly been interpreted on the basis of empirical evidence. This review treats scattering and absorption by populations of cells and large subcellular structures (particles) in dilute suspension. These particles are generally larger than the wavelength of the light; they are in the Lorenz-Mie light-scattering domain. We omit small particle (molecu­ lar) scattering, quasi-elastic scattering (which reveals particle size, etc, from diffusion theory), single particle scattering techniques, and effects that involve the measurement of linear or circular polarization. We consider only certain fundamental problems in scattering by populations that have received too little attention.

Lateral beam collimation of a phased array semiconductor laser

Abstract: The lateral near‐field and far‐field radiation patterns of a phase‐locked array of gain‐guided semiconductor injection lasers are studied. These lasers exhibit a lateral far‐field beam divergence full width at half‐maximum (FWHM) of 1.5° up to 200 mW of output power per facet. Greater than 60% of the laser output power is concentrated in a low divergence beam at this high optical power. Catastrophic mirror degradation of the laser occurs at ≊250–270 mW cw per facet.

Polarization-insensitive optical switch and multiplexing apparatus

Abstract: Polarization-insensitive optical switch and dual channel carrier multiplexer includes a polarization beam splitter for receiving an input collimated beam which has arbitrarily polarized components, splitting the beam into the two components. One of the components is rotated by a 1/2 wave plate so as to yield a polarized beam which is polarized in the same direction as the other beam. The two polarized beams are then applied to a polarization sensitive interferometric multimode fiber optic switch and modulator. The output of the interferometric multimode fiber optic switch and modulator contains two beams, both polarized in the same direction. One of the beams is rotated ninety degrees by a 1/2 wave plate, and the two mutually perpendicularly polarized beams are then recombined by a polarization beam splitter operated in reverse to yield an output beam containing mutually perpendicular components.

Electronically tuneable light source

Abstract: An electronically tuneable light source includes a source (10) of white light, an acousto-optic modulator (16) which includes a transparent medium and means (17) for generating an acoustical wave in the medium, and means for directing the collimated beam of the white light onto the medium at a preselected angle θ/2 to a line which is perpendicular to the direction of travel of the acoustical wave. Interaction of the light beam with the acoustical wave causes diffraction of the light beam. Means (22) are provided for selecting a visible band of the diffracted beam at an angle to the incident collimated beam of light equal to approximately 8.

Detection and imaging of objects in scattering media by light irradiation

Abstract: A method and system are described for the detection and imaging of objects and structures in scattering media using light radiation The medium is scanned with a strongly collimated light beam (2) The light power (Pb) scattered backward from the medium is detected by a receiver (17) and plotted along the scanning path Objects (4) buried in the medium (9) are detected by the differential variation of the received light power Information as to the size, location and depth of the objects can be obtained The illumination by strongly collimated laser light at one or several wavelengths is preferred

Unwanted photon and neutron radiation resulting from collimated photon beams interacting with the body of radiotherapy patients

Abstract: Monte Carlo calculations have been made to determine the energies delivered by photons and neutrons to the human body irradiated by collimated photon beams. The beams were monoenergetic and ranged from 100 keV to 40 MeV. The energy deposition in the body was sorted into two regions: inside and outside the irradiated volume. Most of the results obtained were for a beam size of 100 cm/sup 2/ although some calculations were also made for 600 cm/sup 2/ beams. The effect of beam size on energy deposition in the two regions was investigated for /sup 60/Co gamma rays. Graphs are presented which give the integral doses delivered by neutrons and photons to the two regions for therapy beams of various energies. These graphs can be used to calculate the integral doses which are delivered inside and outside the treatment volume for photon spectra from most medical accelerators. Calculations of energy deposition were also made for the spectra from two particular accelerators. These were done using Monte Carlo as well as by simply ''folding'' the spectra into the results for monoenergetic photons. The results obtained by both methods were in good agreement and indicated that the integral doses deposited outside the treatmentmore » volume by neutrons are more than two orders of magnitude smaller than those deposited by scattered photons.« less

Formula for the density of tangent rays over a caustic surface

Abstract: The geometrical flux density (irradiance) is singular over caustic surfaces and, therefore, cannot be used effectively as a measure of the concentration of rays at or near the caustic surfaces A finite substitute measure, the density of rays tangent to the caustic, may be obtained by dividing an element of incident flux by the area of the caustic formed by the associated rays This gives a measure of the energy density over different regions of the caustic As an example, the ray density over the caustic is evaluated for collimated light reflected from a spherical mirror A similar calculation is performed for collimated light refracted by a plano-convex singlet lens General formulas are presented for computing the ray density over the caustic for reflection of meridional rays by an aspheric surface Also analytical and numerical algorithms are given for evaluating the ray density over the caustic in a multiinterface optical system

A device for dispersing light rays issuing from a light guide

Abstract: A simple compact robust device for dispersing light rays issuing from a light guide. The device has an elongated body of a rigid transparent material, an end of the body being tapered to define an inclined nearly conical peripheral surface, so that those light rays, entering into the body at a small angle with respect to the longitudinal axis of the elongated body, are reflected back into the body by the internal boundary of the inclined surface and are directed to propagate at a larger angle, whereby collimated light rays, issuing from the light guide, are dispersed. The device is particularly useful in lighting systems utilizing solar radiation as a light source.

Method and apparatus for measuring optical properties of materials

Abstract: A method and apparatus for measuring optical properties of materials such as optical rotation, depolarization and absorption includes a light source emitting a primary beam of light that is monochromatic, collimated and plane-polarized and a sample cell through which this beam is passed. The primary beam is split into at least two components by a beam splitter and each component is passed through an analyzer, such as a prism. The two analyzers have polarizing axes oriented at a non-zero angle with respect to one another and at pre-selected angles with respect to the plane of polarization of the original beam. Signals corresponding to the intensities of the components are produced by detectors and then the signals are amplified, digitalized and processed to yield the optical properties. A third test component may alternately be split from the primary beam after it has been passed through the sample with this test component also being detected and processed. A reference component may be split from the primary beam before it is passed through the sample, and the reference component is detected and processed. Existing optical components are assembled to accomplish these steps, and a monochrometer may be used with a selected light source to vary the wavelength of the primary beam.

Significance of higher-order multiple scattering for laser beam propagation through hazes, fogs, and clouds: errata

Abstract: An approach is outlined for computing the different orders of scattering in any medium that possesses a phase function with a strong forward peak. Computations are done for the case of a Gaussian laser beam incident on such a medium. The formulation adopted does reproduce the natural divergence of general Gaussian beams without the need to assume the presence of point sources or the need to assume perfectly collimated beams within the region of interest. Results are discussed for the case of water cloud particles with a strongly forward-peaked phase function for the incident laser radiation.

Apparatus for transformation of a collimated beam into a source of _required shape and numerical aperture

Abstract: A laser light source for a high resolution projection lithography system and transforming optical apparatus which transforms the laser light into an optically equivalent self-luminous curved line source. The transforming optical apparatus comprises a two-dimensional array of fly's eye lenses positioned to intercept light from the light source and to produce a series of point sources having a selected numerical aperture. An optical fiber array is positioned so that the imput end of each fiber receives the light output from one of the lenses in the array. The position of the fibers is chosen so that light from the lenses underfills the fibers to preserve the numerical aperture. The output ends of the fibers are arranged in position to produce a curved line source of a desired shape. Alternate embodiments are described in which lens arrays can be selectively positioned to change the numerical aperture of the transforming optical apparatus.

Electrochemical photoetching of compound semiconductors

Abstract: A procedure is described for electrochemically photoetching n-type and intrinsic compound semiconductors. The process involves applying a potential to the compound semiconductor while it is in contact with an electrolytic solution and irradiating the surface to be etched with light in a certain energy range. By suitable adjustment in the potential, electrolytic solution composition and light energy, the etch rate is made proportional to the light intensity. By suitable variation in light intensity and light-ray direction, various geometrical features can be made on the surface of the compound semiconductor. For example, a hole with straight sides can be made in the compound semiconductor by use of a light spot and parallel (collimated) light rays. An advantageous application of this process is the fabrication of a photodiode with a hole in the center for use in bidirectional communication systems and to monitor power output for optical communication sources. The advantage of this process is that no damage occurs outside etched hole so that a maximum area of the photodiode remains active for detecting incoming radiation. Another advantage of the process is that etching will stop where the material becomes p-type so that etching can be made to stop automatically at a p/n junction.

Comparison of Reconstruction Algorithms for an Electronically Collimated Gamma Camera

Abstract: The performance of different iterative algorithms has been studied for reconstructing emission images of single gamma emitters, using a new gamma camera based upon an electronic method of collimation. Adaptations of the ART, SIRT, and Iterative Least Squares algorithms have been studied. The algorithms have been compared via simulation with respect to the rate of convergence, sensitivity to noise, resolution, and contrast of the reconstructed image. Results have also been obtained with experimentally measured data from a point source of Tc-99m.

Electro-optical level detector

Abstract: Level detection apparatus for determining the depth of a variable surface with respect to the apparatus is disclosed. The device includes a scanning source which causes an intense, collimated beam of light to move across the surface to be detected. First and second spaced detectors sensitive to light reflected from the surface are located at opposite sides of the scanning source and lie in the plane of the scanned beam so that the source directs light from the reflecting surface onto first one and then the other of the detectors. A circuit responsive to the receipt of the reflected beams by the first and second detectors produces first and second signals which will be spaced in time in accordance with the depth of the surface to be measured. An index signal is generated in synchronization with the rotation of the scanning source, and a comparator circuit is provided for comparing the time delay between the two detector outputs, whereby a level output signal proportional to the depth of the surface is produced.

Stationary light source electrophotographic copier

Abstract: A stationary light source electrophotographic copier wherein collimated light from the source is directed to a scanner having upper and lower document illuminating reflectors comprising thin members of negligible mass maintained under tension. The lower reflector includes a plurality of generally horizontal slats disposed in a generally vertical array. Heat from the stationary light source is used to dry or fix copies.

Variable aperture collimator for high energy radiation

Abstract: An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

Apparatus for measuring the characteristics of an optical system

Abstract: An apparatus for measuring the optical characteristics of an optical system includes a light source, collimator means for collimating a beam of light from the light source, a mask means, a means for holding the optical system to be tested between the collimator means and the mask means, a detector, a calculator, and first beam splitting means. The mask means includes at least one mask provided in each optical path following the first beamsplitter means, each having a linear band group consisting of at least two parallel linear bands, with each mask disposed to provide a different orientation for the linear bands.

Measurement of ultrasonic velocity and absorption in liquids up 1.5 GHz by the high-resolution Bragg reflection technique

Abstract: A new UHF ultrasonic technique which is useful for simultaneous measurement of the velocity and absorption in liquids is introduced and described in detail. A ZnO film transducer excites a continuous ultrasonic wave in the test liquid which is illuminated by a highly collimated beam from a He-Ne laser. The light scattered by the sound is detected by an optical heterodyne technique and recorded as variations in the angle of optical incidence with respect to the sound wavefront. The recorded curve is associated with the k spectrum of the sound; the peak and the width give the ultrasonic velocity and absorption, respectively. The accuracy is better than 0.1% for nu and 5% for alpha . The experiment was performed in carbon disulphide and bromoform near room temperature, over a range from 50 MHz to 1.5 GHz. The results are combined with the data obtained by a pulse method and by spontaneous Brillouin scattering to present the ultrasonic spectra over the range from 3 MHz to 6 GHz.

Apparatus for determination of elastic isodynes and of the general state of birefringence whole field-wise using the device for birefringence measurements in a scanning mode (isodyne polariscope)

Abstract: An apparatus has been developed to experimentally determine the state and amount of birefringence in an arbitrary plane within a birefringent body using an entirely new method. Such information can be used to determine the optical anisotropy in solid and liquid bodies, residual and induced stress fields, etc. This apparatus uses a collimated and polarized light beam which scans linearly the plane of measurement within a transparent birefringent or photoelastic object, and a device which collects particular sheets of light scattered along the path of the light beam, the intensity of which is directly related to the state of birefringence at each scattering point at the plane of measurement within the birefringent body. An imaging device produces in the image plane of the apparatus the lines of constant light intensities which are the lines of constant values of accumulated birefringence. For plane stress states in engineering objects such lines are identical with the elastic isodynes and are therefore called photoelastic isodynes. Two independent fields of such isodynes allow the direct determination of all three stress components of the plane stress state and give an additional relation between the strees components. This is the only experimental method which supplies directly four or more independent data on the stress state at each point within the photoelastic object.

A new collimator for cardiac tomography: the quadrant slant-hole collimator.

Abstract: A quadrant slant-hole (QSH) collimator was constructed for myocardial perfusion tomography on a 15-inch large-field gamma camera. This system optimizes the crystal area for multiple-view photon detection while at the same time offering excellent tomographic performance. In addition to the advantages associated with parallel slant-hole collimation, this system's four orthogonal views provide a solution to the problem of patient positioning, namely, proper alignment of the long axis of the left ventricle to the camera. Rapid data acquisition, together with fast reconstruction, make the QSH system a practical approach to tomographic imaging of the myocardium.

Collimation of ultrasonic linear array transducer

Abstract: The beam characteristics of individual array elements of a linear transducer array are altered by collimation of ultrasonic waves using critical angle effects. A phased array transducer for a medical imaging system with a 90° image sensor has a collimator which is a thin sheet of polyethylene. Acoustic waves whose angle of incidence is greater than the critical angle are totally reflected. Insignificant ultrasonic energy is generated outside of the imaged sector and there is a modest insertion loss over the acceptance region.

Apparatus and method for sizing particles

Abstract: The disclosed invention employs an optical heterodyne technique that depends upon coherent detection of phase modulated light from individual particles, and does not depend on measurement of light scattered at a specific angle from particles. A collimated coherent beam of light is generated and separated into a subject beam and a reference beam. The subject beam is focused at the inspection region and light is gathered from the inspection region. The gathered light and the reference beam are combined and a photodetector is responsive to the combined light for producing an electrical signal representative of the combined light. The phase shift of light scattered from an individual particle passing through the inspection region is then determined by measuring the power in the phase modulated sidebands of the electrical signal. The phase shift is indicative of the size of the particle passing through the inspection region.

High frequency light modulator

Abstract: An electrooptic device for controlling the intensity of a monochromatic light beam comprises a transparent element having opposed planar surfaces operable to reflect a collimated light beam alternately from the two surfaces. A plurality of semiconductor structures contact one surface of the device at regions where the collimated light beam reflects from that surface. Each semiconductor structure includes a thin layer of a material such as a metal in contact with the planar surface of the transparent element and a semiconductor material adjacent to the metal layer. A voltage source provides a potential between the metal layer and the semiconductor material of each structure to separately alter the charge density in the semiconductor material of each structure to affect the degree of coupling between the light beam entering the device and surface plasmon waves generated within each structure. The device is operable as a signal mixer or an optical logic switching device.