Showing papers on "Beam splitter published in 1975"

High brightness full color image light valve projection system

Abstract: There is disclosed an electro-optical system for real time projection of very high brightness, full color pictorial images from television or other program sources onto a large display screen from a set of three reflection type AC driven field effect mode birefringent liquid crystal light valves each of which modulates a primary color component video image onto a collimated beam of polarized light of a given primary color by modulating the polarization state thereof. In order to achieve very high brightness without overheating the system it is necessary that none of the optical elements forming the projection beam optical system absorb light in carrying out their function. Hence all projection beam optical processes are non-absorptive to first order. The light valves are devices that receive and reflect projection light from an independent high power light source while modulating onto the reflected light video images derived from a low level light source such as a cathode ray tube. The modulation onto the projection beam is achieved by modulating the state of polarization thereof. One such device is used for the red portion of the video image, a second for the green portion and a third for the blue portion. The optical system derives light from a white projection light source, polarizes it, splits it into the three primary colors, directs the three colored beams to the three light valves respectively for image modulation, collects the light that has been modulated by the light valves, recombines the three beams, and projects them onto the screen with sufficient registration to create full color range for the full color image. The optical system uses only a single projection lens and a single polarizing/analyzing beam splitter/recombiner and suitable dichroic mirrors. There is thus provided a simple, compact low weight, high brightness and high efficiency full color light valve image projection system for the projection of high brightness, full color, real time dynamic or static imagery which may include provision for overlay legends or other information as well as possible steroscopic or three dimensional perception by the viewer.

Coupled-wave theory for multiply exposed thick holographic gratings

Abstract: A coupled-wave analysis is given for Bragg-angle diffraction of light within a thick holographic emulsion containing two incoherently superimposed phase gratings with a common Bragg angle. Algebraic formulas are given for the amplitude of the coupled diffracted waves. Applications to holographic multi-beam splitters and beam combiners are given and experimental verification is discussed.

Space-invariant achromatic grating interferometers: theory.

Abstract: A general analysis of an n-grating interferometer under various conditions of illumination is presented, where n = 1,...,4. Conditions for fringe localization and effects of misalignment are given. The lesser known phenomenon of the imaging of a grating by a second grating is described from which the fringe forming capacity of multiple-grating interferometers stems; this can occur regardless of the coherence of the source.

Propagation characteristics of a partially metal-clad optical guide: metal-clad optical strip line.

Abstract: Experimental investigations of the partially metal-clad optical guide were performed. The optical guide consisted of a silicon substrate, an SiO2 low index dielectric layer, an Al2O3 high index dielectric layer, and a partial cladding layer of Al. The far-field patterns of the output beam from the second prism coupler were consistent with the calculated transverse field distributions using the effective index-of-refraction method. The experimental results on the coupling angles, confinement at the curved section, and attenuation constants are also reported.

Reflection elimination system

Abstract: A device which eliminates unwanted light rays and permits passage of desired light rays. For the purposes of this specification, the desired light rays are those which originate on a first side of a material capable of effecting light passage, and which pass through the material to a second side. Undesirable light rays are those originating on the second side of the material, which pass through the material to the second side of the material. The material, in the embodiment illustrated, is a beam splitter intended to present a desired scene to an observer. The preferred embodiment includes a linear polarizer and a quarter wave retarder which impart an elliptical polarization to the undesired light rays. The polarizer and the retarder are arranged with respect to one another and to the beam splitter so that undesired light passing through the polarizer, retarder, and the beam splitter, and which is reflected back through the beam splitter to the polarizer will return, after reflection, with the same ellipticity but with orthogonal orientation. A method for determining the ratio components of light polarization when light is transmitted through a material, reflected and returned through the same material.

Laser photocomposition system and method

Abstract: Type characters are formed on a photo-sensitive surface by projecting a laser beam directly onto the photo-sensitive surface while moving the beam rapidly upwardly and downwardly, moving the beam steadily in a horizontal direction, and blanking the beam at selected times during the vertical movements. The horizontal movement gives horizontal dimensions to the characters and proportionally spaces them from one another to form composed lines of characters. The blanking of the beam is accomplished by providing a barrier near the optical path of the beam, and using an acousto-optic modulator to rapidly deflect the beam out of its path and against the barrier. A programmed computer is used to store information regarding the start and the stop of each blanking interval for each vertical stroke forming each of the characters of a substantial number of fonts of characters. An optical-electric feedback system is used to indicate the precise position of the laser beam relative to the photo-sensitive surface. This feedback arrangement includes a beam splitter for capturing a portion of the laser beam and projecting it onto an optical grating which is located in a fixed spatial relationship to the photo-sensitive surface. A photo-electric detector is used to detect the position of the laser beam and provide an electrical signal to time the operation of the vertical scanning and blanking devices. The speed of the machine preferably is increased by detecting the height of the characters in a line to be composed and, if the maximum height of any character is below a pre-determined level, then reducing the vertical scan distance traveled by the laser beam while increasing the horizontal and vertical scan rates.

Laser doppler velocimeter

Abstract: A laser doppler velocimeter for measuring one or more velocity components of a moving material, fluid or solid, using a single set of optical focusing elements. A unique two component beam splitter provides multiple pairs of parallel beams, one pair from each input radiation beam from a given laser source. Each incident radiation input beam is separated by means of a selectively transmissive coating on one of the roof faces of an Amici prism into a first beam comprising substantially all of the polarized component parallel to the plane of incidence (P polarization) and one-half of the polarization component normal to the plane of incidence (S polarization), and a second beam comprising one-half of the S polarization component alone. At the measuring point, the two beams interfere, with the S components producing a differential doppler frequency superimposed on a non-doppler pedestal, while the P component contains only the non-doppler pedestal. The detector beam splitter directs the P polarization component to one radiation detector and the S polarization component to the remaining detector. The analog electrical equivalent signal to the optical P component signal is electrically subtracted from the electrical analog equivalent to the S component signal, the pedestal is removed, and this signal is divided by the P component signal to yield a signal having the pure doppler differential frequency information. The invention provides dual beam redundancy, extremely simple alignment, and two velocity measuring ranges.

Intruder alarm arrangement for an optical communication system

Abstract: An intelligence modulated optical beam is injected into an optical waveguide through a beam splitter. At the output end of the optical waveguide the optical beam has a portion thereof transmitter through a partial reflector to a detector or receiver with a portion of the optical beam at the output of the waveguide being reflected back into the waveguide with the reflected beam being reflected by the beam splitter to a correlator. A replica of the intelligence of the injected optical beam delayed an amount equal to the round trip transit time of the optical beam is supplied as the other input of the correlator. The delayed replica of the intelligence of the optical beam and reflected optical beam are correlated to produce an output from the correlator proportional to the attenuation or intensity of the reflected beam. When the output of the correlator falls below a given value, an alarm is actuated indicating that an intruder has intercepted intelligence of the optical beam transmitted through the waveguide.

Magneto-optical digital light deflector

Abstract: A switching device for switching an optical beam between first and second outputs each associated with first and second paths in a thin-film optical wave guide supported on a substrate. Switching occurs by reason of mode conversion in a first or second path as determined by the direction of a variable magnetic field. A common optical path is defined, in said wave guide, by a first optical coupler, for coupling an optical beam into or out of said wave guide, and a beam splitter. First and second optical paths are defined, in the same wave guide, between the beam splitter and second and third couplers each co-linear with said beam splitter. At least a portion of each of said first and second optical paths include means for periodically varying the magnetization in said path. The wave guide is subjected to a d.c. magnetic field in the plane of the wave guide and at an angle with respect to both said first and second paths. Preferably the first and second paths are perpendicular and the d.c. field makes a 45° angle with each of said paths. A variable magnetic field is superimposed on the d.c. field and is directed perpendicular to the d.c. field, in the plane of the wave guide. The variable magnetic field may be energized in one of two senses, 180° apart, each, of course, perpendicular to the d.c. field direction. Analyzers may be located adjacent the second and third couplers to comprise the outputs referred to above.

Thin‐film beam splitter and reflector for optical guided waves

Abstract: We report the fabrication and operation of a new and simple beam splitter and reflector for thin‐film optical guided waves.

Velocity profile measurements in a liquid film flow using the laser Doppler technique

Abstract: The optical arrangement for a laser Doppler velocimeter is described. A rotating radial diffraction grating has been used as beam splitter in order to shift the laser light frequency. The advantages are that a high spatial resolution can be obtained and that it allows the removal of the pedestal in the Doppler signal. It also provides a method for determining the position of the measuring volume relative to the wall of the test section. Experimental results are presented.

Method and apparatus for splitting a beam of energy

Abstract: A method of forming two diverging beams of energy from a single beam of energy including the steps of splitting the single beam of energy into an externally reflected beam and an internally transmitted beam at a first surface on a wedge shaped energy beam splitting device; splitting the internally transmitted beam into an internally reflected beam and an externally transmitted beam at a second surface of the wedge shaped energy beam splitting device, and substantially totally reflecting the internally reflected beam between the first and second surfaces until the internally reflected beam reaches an end of the wedge shaped energy beam splitting device. The above method may further include steps paralleling the above steps wherein two diverging beams of energy are formed from a second beam of energy impinging on the second surface and then combining the two diverging beams with the two diverging beams formed from the beam of energy split by the first surface, to form first and second combined beams. The preferred apparatus for performing the method is an energy beam splitting device having a first surface for splitting an incident beam energy into an externally reflected beam and an internally transmitted beams, a second surface spaced from the first surface for splitting the internally transmitted beam into an externally transmitted beam and into an internally reflected beam, and the second surface intersecting the first surface at an angle that impinges the internally transmitted beam on the second surface at an angle of incidence that is less than the minimum angle necessary for substantially total internal reflection and impinges said internally reflected beam on the first surface at an angle of incidence that exceeds the minimum angle necessary for substantially total internal reflection. The above device may further be used as a beam combiner by having the second surface split a second incident beam of energy into two diverging beams of energy and combining the two beams produced by the first surface with the two beams produced by the second surface to form first and second combined beams.

Far-infrared thin-film beam splitters: calculated properties

Abstract: Properties of beam splitters for a far ir Michelson interferometer have been calculated for four plastic materials: Surlyn, Aclar, Mylar, and Kapton. Although the materials are birefringent, the averaged optical constants are used; and it is shown that this procedure yields valid beam splitter characteristics.

Precision Beam Splitters for CO 2 Lasers

Abstract: Beam splitters for 10-μm lasers are discussed and then applied to the precision measurement of high average powers. In particular, beam splitter stability has been investigated in various materials over the 20–600-W power range with power densities up to 1 kW/cm2. The absolute beam splitter ratios are given along with the achieved measurement precisions. The semiconductors investigated were GaAs, CdTe, and ZnSe in addition to one alkali-halide KCl. Standard deviations for the beam splitter ratios of 1% over the power range were typical. Absolute ratios agree with the predictions from Fresnel’s equations to 1% or better. The best measurement was made on ZnSe when a standard deviation of 0.4% was obtained for the measurement of a ratio that agreed with a calculation from Fresnel’s equations to better than 0.5%.

The performance of acousto-optic cells for laser-Doppler anemometry

Abstract: The performance of water filled acousto-optic cells is quantified with particular reference to their use for laser-Doppler anemometry. With the cell operating at a frequency of 9.2 MHz, the intensities of the +1 and -1 order beams are shown to account for 76% of the transmitted light intensity for an electrical power input of 0.56W. The influence of the incident angle and the performance of a cell at frequencies close to but different from the fundamental frequency are quantified. Operation of the cells at a frequency of 30 MHz, i.e. close to a third harmonic, is shown to require significantly greater electrical power input but can without introducing thermal connection effects, allow the transmission of a first and zero order beams with equal intensities and a total loss of 8% of the incident intensity. To show that an acousto-optic cell can be used as a beam splitter and frequency shifter, measurements of three components of velocity are reported in the region of recirculation immediately downstream of the centre disc of an annular jet.

Laser system with an antiresonant optical ring

Abstract: Various applications of an antiresonant ring, consisting of a beam splitter and a number of optical reflectors, are disclosed. With a beam splitter having a transmission coefficient t1 and a reflection coefficient r1 where t1 = r1, an optical beam incident on the beam splitter along a first axis is split into two components which circulate around the ring in opposite directions and are recombined to reflect back the beam along the first axis, with none of the beam power being directed along a second axis. The ring can be used as part of the cavity of two otherwise independent lasers, with two separate laser mediums external to the ring, or with a multi-wavelength laser medium in the ring. The ring together with a second-harmonic generation crystal and a dispersive phase shifter in the ring can be used to generate the second harmonic of an optical beam. By proper incorporation of phase shifting means in the ring, optical pulse switching, laser mode locking, and/or laser cavity dumping can be achieved.

Michelson interferometer with frustrated-total-internal-reflection beam splitter

Abstract: An efficient beam splitter for a Michelson interferometer can be made from a pair of prisms, using the process of frustrated total internal reflection. Although the phases and irradiances of the beams reflected and transmitted by the beam splitter depend on the polarization, the phase difference between the two interferometer beams vanishes for all polarizations and the transmittance can be made polarization insensitive by suitable design. The interferometer transmits radiant power within a wavelength band approximately two octaves wide, and rejects all other radiant power. The design, laboratory tests, and astronomical applications of an interferometer for the millimeter and submillimeter regions are discussed. An observation of the day-sky spectrum is presented.

Roll reference system for vehicles utilizing optical beam control

Abstract: Control information for guiding of vehicles such as a missile, projectile or manned vehicle, is carried on an optical beam directed at such vehicle from a ground station. Information for roll stabilization of such vehicle is carried in such beam in the form of a polarized light wave. A polarizing beam splitter which is aligned with the vertical axis of the vehicle and carried thereon receives the beam and provides light outputs from one face thereof which is in accordance with the cosine squared of the angle between the vertical axis of the vehicle (or any other predetermined reference angle thereof) and the polarization angle of the light beam, and from an orthogonal face thereof which is in accordance with the sine squared of this same angle. The light emitted from each of the beam splitter surfaces is transduced to electrical form by means of light detectors and these electrical signals appropriately amplified for use in controlling a roll stabilization system.

Attenuating image extender for multiple imaging system

Abstract: Disclosed is an optical system for dividing a single optical image into two or more geometrically identical images which are contiguous and coplanar in space and which have the same magnification. A beam splitter and a fold mirror divide the original optical path into a first optical path which forms an image from light passing through the beam splitter and a second optical path which forms an image from light reflected from the beam splitter and fold mirror. A displacement block is inserted into the second optical path to move the image plane away from the fold mirror and cause the images formed from the first and second paths to become coplanar. The displacement block is mounted so that it can rotate about two axes so that one image can be positioned precisely adjacent to the other image. By forming the block from two glasses having different absorption characteristics light in the second path is adjustably attenuated.

Optimizing Fourier Transform Spectrometer Beam Splitters for High Efficiency and Minimum Polarization

Abstract: Ideally, the beam splitter in a Michelson interferometer used for Fourier transform spectroscopy must have 50% transmission and reflectance for high efficiency, and this should be independent of polarization. Semitransparent metal layers do not meet the efficiency criterion because of their absorption loss, and multilayer systems required for wide wavelength coverage are difficult to produce in practice. Single layer or thin film beam splitters have thus nearly dominated the field. These beam splitters usually show polarization effects, the avoidance of which is discussed here.

Optical readout for differential laser gyros

Abstract: In a differential laser gyro system including a ring laser in the form of a figure eight incorporated in a solid block, optical readout is accomplished by mounting the readout optics to the block in a manner similar to that employed for the laser optics. The laser optics comprises four mirrors mounted on the outer face of the block, with diagonally opposite faces being parallel. A modulator having plane parallel end faces is incorporated in the laser optical system, and oriented so that readout reflections therefrom occur in a plane at a slight angle to the lasing plane. Readout beam director prisms are positioned on the outer faces of the block adjacent to the laser optic system mirrors, and direct the readout reflections to a beam splitter and then to optical detectors as in conventional readout optical systems. Alignment of the readout system is enhanced by virtue of the fact that both angular and linear adjustments can be made by rotating or translating the readout optics. By virtue of the mounting of the beam splitter on a spherical base, angular adjustment of the beam splitter is provided to assure colinearity of the readout beams at the optical detectors.

Second harmonic analyzer

Abstract: A method and device for determining acentricities in a powder material by illuminating the powder with a collimated coherent light beam of given wave-length which generates a second harmonic in the material. The second harmonic with the fundamental removed by filters is divided by a beam splitter and sent to two photomultipliers -- one of which has a narrow band filter to select only light of one wave-length. If all the light is generated at the second harmonic equal signals are produced by the photomultipliers. If non-second harmonic radiation is produced, a larger signal will be produced in the unfiltered reference channel.

Beam splitter for electron beam machines

Abstract: A beam splitter for electron beam machines with a beam splitter grid which is to be set crossways to the beam and which has a row of cross-pieces running next to one another with uniform spaces for shading the portions of beam striking it, where the cross-piece materials is replaceable in operation by cross-piece material not already acted on by the beam.

Relative flatness measurement of uncoated optical flats

Abstract: A method is described for measuring the relative flatness of uncoated precision optical flats to lambda/1000. The method uses scanning interferometry and can be made automatic fairly readily.

The Design of Two Shearing Interferometers for Studying Refractive Index Distributions near Opaque Boundaries

Abstract: Two wave-front shearing interferometers for the measurement of optical path distributions close to opaque obstacles are described. The introduction of a new beam splitter in one of the interferometers produces an interferogram from which the path differences in the test region can be obtained with higher accuracy. The other interferometer is designed for the investigation of refractive index distributions, where the sensitivity can be greatly enhanced by optimizing the shear of the wave-fronts.

Holographic storage device

Abstract: A holographic storage device which is capable of enabling both recording of information to be stored and retrieving information characterized by a portion of a beam of coherent light being directed onto a sub-hologram of an illumination hologram to create an illuminating beam which is projected on a modulator matrix which creates an object wave that is projected onto the storage medium during a recording operation. The device further includes a detector matrix utilized during the retrieval operation and both the detector matrix and the modulator matrix are separated from the storage medium by transparent bodies having an index of refraction greater than 1. In one embodiment, at least two of the transparent bodies include light splitting or distribution surfaces which split off a portion of the beam passing therethrough, the illumination hologram is preferably a surface relief reflection hologram and a retrodirective mirror is utilized to direct the beam passing through the first beam splitter to a second beam splitter to be projected onto the storage medium. In a second embodiment, the coherent beam of light is projected through a transparent body, the storage medium and received by a retrodirective mirror which directs it on the illumination hologram. In this embodiment, the illumination hologram can be in the same plane as the storage medium and the modulator matrix is a reflective matrix to reflect the modulated object beam back onto the storage medium. In a similar arrangement of the embodiment, the modulator matrix is a transparent matrix and an additional transparent body is arranged on the opposite side thereof with the illumination hologram disposed on opposite surfaces.

A note on the design of laser beam monitors

Abstract: Calculations of the change of the reflectance of the beam splitter of a laser beam monitor resulting from small changes in direction of incidence, polarization, and divergence of the incident beam, are summarized. It is concluded that for angles of incidence less than about 30 degrees these changes in reflectance will not significantly change the responsivity of the monitor, whereas for a beam incident at 45 degrees considerable errors will result. The design and performance characteristics of a beam monitor in which a linearly polarized beam is incident on the beam splitter at 20 degrees are discussed.