Showing papers on "Beam splitter published in 1978"

Interferometer apparatus using electro-optic material with feedback

Abstract: A nonlinear interferometer apparatus is disclosed wherein a Fabry-Perot cavity is substantially filled with an electro-optic material having terminals to which a potential can be applied. A single frequency, single mode, linearly polarized source of optical radiation is coupled into the cavity and a beam splitter at the output of the cavity deflects a portion of the optical energy coming from the cavity. This deflected portion of output optical energy is incident on a photodetector whose output is amplified and connected to the terminals of the electro-optic material. The resulting device exhibits differential gain, and can function as an optical switch, limiter or optical memory element. With sufficient amplification of the detector output, an optical quantizer is provided. By properly adjusting the cavity length and providing a substantially constant optical signal to the input end of the cavity, an amplified replica of an amplitude modulated optical signal applied to the photodetector appears at the output end of the cavity.

Holographic head-up displays

Abstract: There is disclosed an integrated optical design of head-up displays suitable for use in aircraft cockpits and the like. The display system is comprised of a holographic optical element used as the combiner for presenting a direct view of the exterior on which are superimposed image signals generated by a source device such as a cathode ray tube and transmitted to the combiner through an optical system including a relay lens containing tilted and decentered optical elements to compensate for the aberration present in the holographic optical element. There are further disclosed four relay lens design forms particularly suited for use in the design of such holographic head-up displays. The disclosure includes integrated designs in which (a) the holographic element may or may not be constructed with aberrated wavefront and (b) a beam splitter is incorporated for insertion of a stand-by sight, possibly also being tilted for the correction of aberrations.

Phase nulling optical gyro

Abstract: A beam of light is split and introduced into different ends of a light path whose rotation is to be sensed. At least one frequency shifter is placed in the light path to affect the frequency difference of the two beams so as to introduce or adjust a nonreciprocal phase shift. The beams are then mixed back together and the resultant beam is detected and analyzed by suitable circuitry to provide an output indicative of rotation of the light path.

Artificial and solar lighting system

Abstract: A sunlight collector, containing a Fresnel lens, is mounted on the roof of a building and tracks the sun during daylight hours. A concentrated beam of sunlight is directed through a light transmission channel to locations within the building where the light is distributed. The transmission channel utilizes a focusing lens for further concentrating the solar beam, refocusing lenses for correcting divergences in the beam, reflectors for redirecting the beam, and beam splitters for distributing the beam into light fixtures located throughout the interior of the building. The light fixtures contain filters for controlling the intensity and spectral content of the incoming beam, and optical elements for dispersing the beam. Additionally, the fixture contains rigidly mounted fluorescent tubes, providing artificial light, which are automatically energized when the solar light is insufficient for lighting purposes. A diffusing element is used for uniformly radiating both the artificial and the dispersed solar light from the fixture into the building interior.

Beam-splitter Coatings for Producing Phase Quadrature Interferometer Outputs

Abstract: The measurement of displacement using a Michelson-type interferometer requires a beam-splitter coating that ideally produces two signals in phase quadrature. In this paper a number of beam-splitter designs utilizing thin metal films are discussed. Problems associated with film deposition and monitoring are considered, and it is shown that, using conventional techniques, the required phase difference can be readily achieved using, for example, combinations of gold, chromium and aluminium films.

Distributed Bragg deflector: a multifunctional integrated optical device.

Abstract: The properties of wide-angle integrated optical Bragg deflectors which utilize slab-coupled optical waveguides, are analyzed. Specifically considered is the interaction that occurs, via the intermediary of a periodic waveguide perturbation, between an incident wave guide within the core region of the structure and a Bragg deflected beam guided within the slab region of the structure. The deflection efficiencies and far-field deflected-beam intensity patterns characteristic of this device configuration, which we term a distributed Bragg deflector or DBD, are derived for both T.E.-polarized and T.M.-polarized incident waves and for deflection angles between π/4 and 3π/4 rad. Following these derivations, discussion is made of the potential device applications of the basic DBD structure, including its use as an integrated optical modulator, polarizer/analyzer, beam divider, beam deflector, and intrawaveguide beam expander.

Photoelectric detecting device

Abstract: A photoelectric detecting device in which a photoelectric detecting system for scanning a surface to be inspected by a light beam and for receiving the light from the inspected surface by a photoelectric detector is partly common to an observation optical system for illuminating the inspected surface with an illuminating light and for observing the inspected surface. The device has a dichroic mirror and a polarizing beam splitter, whereby photoelectric detection is effected without loss of light and without adverse effect of the illuminating light.

Mylar beam-splitter efficiency in far infrared interferometers: angle of incidence and absorption effects

Abstract: Absorption and complete multipath interference have been included in the calculation of the modulation efficiency of a far i.r. Michelson interferometer with 25-μm and 100-μm Mylar beam splitters over the range of wavenumbers between 20 cm−1 and 125 cm−1 for angles of incidence between 45° and 80°. These results show that optimum performance of an interferometer in terms of highest and most uniform modulation efficiency for unpolarized radiation will be obtained by selecting the beam-splitter thickness to cover the wavenumber range of interest within the first interference lobe and by utilizing higher angles of incidence than the mechanically convenient 45°. Practical constraints will usually limit this angle to a value somewhat less than the optimum of about 75° for Mylar beam splitters.

Optical gyroscope system

Abstract: An optical gyroscope is described of the type which passes light beams in opposite directions through a single mode fiber optic wave guide that extends in a circle or coil, and which enables measurement of rotation rate of the coil by measuring the relative phase shifts of the beams by interferometric techniques, wherein simplification and enhanced accuracy are obtained. Beam splitting and phase shifting of the light is facilitated by utilizing brief pulses of light and by using light-controlling devices which are operated for a brief time only when the light pulse passes in one direction through the device but not at a different time when the pulse is passing in the opposite direction through the device. High accuracy in rotation measurement is achieved at both very slow and very fast rotation rates, by alternately operating the system so that at zero rotation the interfering waves are alternately 90° out of phase and in phase. Linear polarization of the light beams is maintained by coiling the full length of the optic fiber in a single plane so that bending stresses induce a birefringence in the waveguide, thus altering the propagation constants of the two polarized modes and decoupling them.

Coherent optical correlator

Abstract: Reference scenes stored in a filter set containing an array of sets of suimposed, holographic, matched filters are optically correlated with input images displayed on an optically-addressed, liquid crystal, light modulator 34. In operation, a selected laser diode is energized to direct a polarized light beam through the collimating lens L1 to the reflecting surface of a polarizing beam splitter 35. After reflecting off the beamsplitter surface, the beam is expanded by positive lens L2 and passed to the liquid crystal modulator. There it is modulated by the input image and reflected; after which it is recollimated by positive lens L2, transmitted by the beamsplitter, and directed to a particular array location of the filter set dependent upon which particular laser diode is energized. The filter set is positioned to be in the back focal plane of lens L4 so that the Fourier-transform of the input image is incident on the particularly located, superimposed matched filter at 31. If the Fourier transformed input image corresponds to one of the superimposed matched filters the incident light beam is diffracted by that particular hologram matched filter to form a spot of light at a predetermined array location of a detector array. The optical correlator finds use as a terminal guidance system in guiding a missile to its target.

Laser dimension gauge

Abstract: A laser gauge to measure a dimension of a workpiece is disclosed wherein a laser beam is directed through a beam splitter to a rotating mirror at the focal point of a parabolic mirror. This rotating mirror causes the laser beam to scan the parabolic mirror and establish a series of parallel laser beams emanating from the parabolic mirror and directed toward the workpiece which may be a hot forged bar or other such workpiece in a hostile environment. First and second laser beam paths lie immediately adjacent opposite sides of the workpiece and are reflected back to the parabolic mirror along the same beam paths by a retroreflective surface. The laser beams are reflected by the parabolic mirror and rotating mirror to the beam splitter whereby they are reflected to a photodetector. A microprocessor is programmed to determine the dimension of the workpiece in accordance with the positions of the rotating mirror which establish the first and second beam paths. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Light absorption device for the prevention of stray light in particular in a phototypesetter

Abstract: A phototypesetter has an optical path including a beam splitter intersecting the main light path and an auxiliary light path for reflecting the auxiliary light path into the main light path. An absorption element with a concave front surface is mounted behind the beam splitter to absorb the non-reflected light from the auxiliary beam. Additionally, the concave surface directs the nonabsorbed light to a light absorbent body.

Fiber optics duplex module

Abstract: A duplex module for simultaneous bidirectional transmit-receive communication with the end of an optical fiber or fiber bundle. The end face of an optical fiber in optical coupling registry with one end of a common bidirectional transmit-receive optical path is tilted to divert any transmit signal back-reflected from such end out of such path. The other end of the transmit-receive path is affiliated with signal receiver and transmitter means via a beam splitter.

The Holographic Pancake Window TM

Abstract: The Farrand Optical Co., Inc. PANCAKE WINDOWTM optical simulator is a very fast, large aperture magnifier which can present to the observer a displayed image at optical infinity. The superb optical quality of this magnifier is due to the fact that reflective, and not refractive elements are used in this system. The unique configuration of this on-axis reflective system, and the optical properties of its elements will be presented. Also, its latest improvement incorporating a spherical holographic beam-splitter mirror will be discussed.

Laser radar tracking system

Abstract: A high precision laser radar tracking system is described. Targets which can be tracked include diffuse passive targets, specular passive targets and optical transponders. The base section of the system is fixed relative to the upper section which can rotate through 360°. The lower section has a laser beam generator, optical signal detector system with a beam splitter/reflector and the upper section has three moveable reflectors one of which acts as a trackable, transmitter/receiver aperture. The system of the invention incorporates techniques utilizing the advantages that emanate from the combination of a laser system and an optical radar system.

Nonlinear optical apparatus using fabry-perot resonators

Abstract: An optical apparatus which provides a nonlinear characteristic between input and output amplitude levels is disclosed. A single frequency linearly polarized single mode light beam having amplitude variations that are to be acted upon is coupled to a Fabry-Perot interferometer (10) having two mirrored ends (11 and 12) and substantially filled with an electrooptic material (13) having electrodes (14 and 15). A beam splitter (21) is positioned and oriented so as to deflect optical energy that is reflected from the cavity into a photodetector circuit (22 and 23) whose output voltage is applied to the electrodes of the electrooptic material. Adjustment of the cavity length provides a wide range of nonlinear characteristics including some that permit the apparatus to be used as a bistable memory element and others which permit the device to be used as a clipper for all input power levels below a predetermined threshold level.

Surface profile measurement and angular deflection monitoring using a scanning laser beam: a noncontact method

Abstract: A noncontact method for measuring the surface profile of a reflecting surface is presented. The scheme is based on the measurement of the phase difference between a surface reflected laser beam and a reference beam. Both beams are scanned past a photodetector by means of a rotating beam splitter. The slope of the surface at various points is electronically obtained, and then the surface profile in a plane is determined by direct integration. The accuracy of the method falls between the more elaborate interferometric techniques and mechanical contact schemes. A complete theoretical analysis of the method is presented as well as the results of various experimental tests.

Acoustooptic beam deflection for spatial frequency multiplexing in high speed holocinematography.

Abstract: Four holograms are recorded superimposed on the same plate at maximum repetition rates of about 10 kHz. A multiply Q-switched ruby laser produces the series of coherent light pulses for hologram exposure. Image separation of different holograms is achieved by spatial frequency multiplexing. The reference beam direction is altered by a unique acoustooptic beam splitter and deflector unit. The operating principle is a sound pulse-light pulse interception technique. Only one ultrasonic transducer is necessary. The quality of the holograms is demonstrated by the reconstructed images taken of laser produced cavitation bubbles following optical breakdown in water.

Automatic focusing apparatus

Abstract: An automatic focusing apparatus includes a lens for leading a laser beam onto a sample surface at a predetermined incident angle, a beam splitter to divide the reflected beam from the sample surface in accordance with the vertical shift thereof, a pair of photo diodes to respectively receive the divided beams and produce electric signals, a differential amplifier to produce a differential signal between the electric signals and a mechanism to vertically shift the stage by means of the differential signal to automatically focus a lens system on said sample surface.

Time-reversed replication of a wave front

Abstract: An apparatus and method for creating a time-reversed replication of an optical wave front. More specifically, an apparatus and method is disclosed in which a non-linear medium having counter-propagating monochromatic optical waves passing therethrough generates a time-reversed replica of an incident wave, the generation being due to non-linear refraction within the medium. As a monochromatic light-ray beam source irradiates an inhomogeneous, nonabsorbing medium, (e.g., a frosted pane of glass), the wave front of the source beam is broken up during transmission therethrough so that any image information contained within the source beam is unrecognizable from the other side of the frosted glass. According to the present invention, this unrecognizable image, when directed into the non-linear medium containing the counter-propagating optical waves is reflected back as a time-reversed wave due to the non-linear refraction of the medium. When this reflected wave irradiates the same inhomogeneous medium, the source beam is recreated on the source beam side of the frosted glass. A beam splitter then isolates the reconstructed reflected wave from the source wave.

Photographic background device

Abstract: A photographic background device enables a photographer to include a scene reproduced on a film transparency as background for photographed subjects. A transparency is illuminated while a beam splitter mirror directs light from the illuminated transparency to the camera lens, while allowing light from the subject to pass through the mirror to the camera lens. A movable lens system of positive power is provided to allow the transparency image to appear in focus at the lens. Vignetting is alleviated by locating a concave mirror on the side of the beam splitter opposite the side on which the movable lens system is located. In this manner, the illuminated film transparency image will pass through the beam splitter, be reflected by the concave mirror back to the beam splitter and be reflected from the beam splitter to the camera lens.

Apparatus for detecting the presence of a specific substance in a gas stream

Abstract: An apparatus for detecting the presence of a specific substance in a gas stream is disclosed. The apparatus comprises a sensing chamber adapted to receive a test paper which is subject to coloration when contacted by a specific substance in a gas contained in the sensing chamber, means for generating a light beam and directing it toward the test paper in the sensing chamber, a light beam sensing device responsive to the extent to which the test paper in the sensing chamber undergoes coloration in response to exposure to the specific substance in the gas stream, an amplifier connected to the light beam sensing device for providing an output voltage which is proportional to the coloration of the test paper, and means connected to the amplifier for providing an output signal which is an instantaneous indication of the concentration of the substance to be monitored, comprising a signal conditioning circuit connected to the amplifier for providing an output which is a linear function of the cumulative amount of the substance to be detected contacting the test paper, and a differentiator responsive to the output of said amplifier for deriving the instantaneous concentration of the substance in the gas stream. The apparatus is further provided with a beam splitter for dividing the light beam into two separate beams, one directed toward the test paper in the sensing chamber and the other toward a variable optical density filter, and a second light beam sensing device responsive to the transmittance of the variable optical density filter. The amplifier is responsive to the two light beam sensing devices for providing an output which is a function of the ratio of the light sensed by the two light sensing devices irrespective of the light source intensity variations. An automatic zero adjustment device is also provided for resetting the output of the amplifier to zero prior to taking measurements.

Apparatus for detecting an output image of an optical correlation

Abstract: A coherent optical correlation system produces an output signal in the form of a beam of light which if focused onto an output plane would produce a spot of light somewhere in that output plane. To detect the position that spot would have in the output plane, the output beam is formed into two parts by a beam splitter and each part is passed through a multiple image diffraction grating arranged mutually at right angles to thereby form a linear array of spots parallel to the x and y axes of a correlation output plane. Each series of output spots illuminates a photodiode in a linear diode array thereby identifying the x and the y coordinates of a correlation image.

Semiconductor laser light source

Abstract: PURPOSE:To treat the composed flux of light with an anamorphic optical system by arranging the p-n junction of a semiconductor laser in parallel with a polarizing beam splitter and by arranging a 1/2 wavelength plate between one semiconductor laser and the polarizing beam splitter. CONSTITUTION:The lights from two semiconductor lasers 1 and 5 are overlapped by a beam splitter 4 and are forcused upon a focal plane 9 by means of condensing optical systems 7 and 8. The respective p-n junctions of the lasers 1 and 5 is arranged in parallel with the splitter 4 such that the polarizing plane is turned at 90 degrees between the laser 1 and the splitter 4. By the actions of the lenses 7 and 8 constituting the anamorphic condensing optical system, a generally round spot 10 can be formed on the focal plane 9.

Laser device with intraresonator harmonic generator

Abstract: A laser device for generating frequency-doubled laser pulses at maximum eciency A laser rod is optically pumped to radiate unpolarized light at 1064μ wavelength for transmission within a ring-type resonator defined by a flat mirror and a turning prism The light from one end of the rod is linearly polarized by a beam splitter into two parallel beams of orthogonal components which are transmitted through an 0532μ output mirror, a frequency doubler phase matched for one component, and a Q-switch, to the turning prism for return along the beam of the other component to the beamsplitter The output mirror, doubler and Q-switch are substantially ineffective during the pumping cycle, and because the component beam axes are reversed, the light does not return to the rod for stimulating light emission After peak level pumping, however, the Q-switch is biased to rotate each component one quarter wavelength and return the components to combine and reenter the rod for stimulated light emission The frequency doubler, now receiving high power radiation, transforms a portion of the returning 1064μ component to a 0532μ component which is then reflected out of the resonator by the output mirror

Optical system for use with apparatus for contouring surfaces with coherent light

Abstract: An optical system having a spherical mirror (34 used to collect light from the surface of a turbine blade (141 or the like which is to be contoured. The spherical mirror (34) is located at an equal optical distance from both the test specimen and the linear diode array (36) so that it operates at a one-to-one magnification ratio The linear diode array (36) is positioned behind the spherical mirror (34) and it receives light focused by the mirror and reflected by a beam splitter (32) through an opening (38) in the center of the mirror None of the optical elements of the inspection system are located in the plane of movement of the test specimen so that even particularly long items such as a helicopter rotor blade can be Identical upper and lower optical systems allow both surfaces of the test specimen to be contoured simultaneously and each system is independently operable and oriented to prevent optical interference. An automatic gain control (40, 31, 42 1 is provided to adjust the optical modulator (22) so that the effective intensity of the spot presented to the diode array is maintained within predetermined limits.

Multilayer optical interference coatings via glow discharge polymerization techniques.

Abstract: The incorporation of an optical-thickness monitor in the plasma reactor allows the fabrication of well tuned multilayer optical interference coatings, the variety and application range of which is constrained only by the limited number of presently known well characterized plasma polymers. The properties and deposition idiosyncracies of several plasma polymers found useful for optical thin films are discussed, and optical performance data for specific beam splitter and antireflection coating designs fabricated from available materials are presented.

Color separation optical apparatus

Abstract: PURPOSE:To reduce the light path and the size, and to simplify the structure, by reflecting from the reverse surface of a beam splittr the light reflected from a dichroic mirror, of the light separated with the beam splitter.