With Birefringent Element Patents (Class 359/256)
  • Patent number: 6055086
    Abstract: A method and apparatus for modulating a light beam in an optical processing system is described. Preferably, an electrically-controlled polarizer unit and/or an analyzer unit are utilized in combination with a spatial light modulator and a controller. Preferably, the spatial light modulator comprises a pixelated birefringent medium such as a liquid crystal video display. The combination of the electrically controlled polarizer unit and analyzer unit make it simple and fast to reconfigure the modulation described by the Jones matrix of the spatial light modulator. A particular optical processing objective is provided to the controller. The controller performs calculations and supplies control signals to the polarizer unit, the analyzer unit, and the spatial light modulator in order to obtain the optical processing objective.
    Type: Grant
    Filed: July 27, 1998
    Date of Patent: April 25, 2000
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: Colin Soutar, Richard D. Juday
  • Patent number: 6049367
    Abstract: The present invention provides a high brightness subtractive color filter formed by an electro-optic modulator positioned between two retarder stacks. The second retarder stack echoes the first retarder stack, having the same sequence of retardances but in reverse order and having an orientation rotated with respect to the first stack. The modulator changes the apparent orientation of the second stack so that, in a first switching state of the modulator the two stacks cooperate in filtering the spectrum of input light, and in a second switching state they vanish, leaving white light. Two or more stages can be used in series, each stage providing independent analog control of a primary color. One preferred embodiment eliminates internal polarizers between stages, thereby providing a full-color display with only two neutral polarizers. Hybrid filters can be made using the filter of this invention in combination with other active or passive filters.
    Type: Grant
    Filed: May 9, 1997
    Date of Patent: April 11, 2000
    Assignee: ColorLink, Inc.
    Inventors: Gary D. Sharp, Kristina M. Johnson
  • Patent number: 6038054
    Abstract: A polarized-light converting elemental device which can produce an accurately unidirectionally and circularly polarized light with a minimized loss of light and a projection-type display device using said unidirectionally-polarized-light converting elemental device are provided. A polarized-light converting elemental device comprises a mirror glass portion consisting of an array of mirror glass blocks each having a first reflecting optical element and a second reflecting optical element and a cholesteric-liquid-crystal glass portion including a cholesteric liquid crystal layer for reflecting either clockwise circularly polarized component or anticlockwise circularly polarized component and transmitting the other. Natural light from the left side is split into two directions by the first reflecting optical element. Light reflected from the cholesteric liquid crystal is reflected by the second reflecting optical element to alter its rotation direction and then transmitted through the cholesteric liquid crystal.
    Type: Grant
    Filed: March 20, 1998
    Date of Patent: March 14, 2000
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Yoshiharu Sakai, Kazuhiro Inoko
  • Patent number: 6034761
    Abstract: An apparatus for measuring displacement information of an object. The apparatus has a light source emitting a light beam, an electro-optical crystal member, a voltage applying system for imparting a predetermined frequency difference between light beams passing through two different areas in the electro-optical crystal member, and a light receiving system for receiving scattered light from the object to which the two light beams emergent from the electro-optical crystal member have been projected. The electro-optical crystal member is disposed so that a light beam from the light source may partly enter the two different areas to form the two light beams to which the predetermined frequency difference is imparted. The displacement information of the object is obtained from the scattered light received by the light receiving system.
    Type: Grant
    Filed: February 11, 1998
    Date of Patent: March 7, 2000
    Assignee: Canon Kabushika Kaisha
    Inventor: Makoto Takamiya
  • Patent number: 6002512
    Abstract: An optical circulator is disclosed that utilizes a polarization rotator comprising a polarization changer (e.g., a properly-oriented half-wave plate) in combination with a pair of latched garnet Faraday rotators. The latched garnet rotators are positioned next to each other and oriented so that one latched garnet rotator provides clockwise rotation and the other provides counterclockwise rotation. The use of latched garnet with a single half wave plate results in an arrangement that is reduced in overall size and does not require epoxy to interconnection the various piece parts.
    Type: Grant
    Filed: October 20, 1998
    Date of Patent: December 14, 1999
    Assignee: Lucent Technologies, Inc.
    Inventors: Ernest Eisenhardt Bergmann, Neal Henry Thorsten
  • Patent number: 5986815
    Abstract: Methods and apparatus for enhancing the performance of reflective LCD systems. The high-contrast color-splitting prism system utilizes a "double-pass" prism assembly. Polarized light enters the prism assembly, is color-split and is emitted as separate colors to reflective imagers which reflect each color in accord with a desired image. The reflected light is passed, once again, through the prism assembly where the separate colors converge and the convergent light is emitted to a projection lens for display of the image on a screen. At least one zero-incidence waveplate compensator is positioned between one reflective imager and the prism assembly. The waveplate compensator effectively decreases the unwanted polarized light entering the prism assembly for the second pass-through, thereby increases the polarization purity of the light that is emitted from the prism assembly to the projection lens to yield a high-contrast projection image.
    Type: Grant
    Filed: May 15, 1998
    Date of Patent: November 16, 1999
    Assignee: Optical Coating Laboratory, Inc.
    Inventor: Brett Bryars
  • Patent number: 5986784
    Abstract: A method and apparatus for overcoming polarization induced signal fading in both heterodyne communication and interferometric sensing. An adjustable birefringent element in series with a linear-polarization beam splitter forms an elliptical-polarization beam splitter. The birefringent element controllably evolves the states of polarization of two input signals thereby controlling the power contribution of each signal onto the orthogonal axes used by the linear beam splitter. When the states of polarization are evolved such that there are equal signal to reference power ratios on the beam splitter axes, subsequent detectors generate a constant, optimum amplitude signal without the need for weighting or decision circuits.
    Type: Grant
    Filed: December 12, 1994
    Date of Patent: November 16, 1999
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventors: Alan D. Kersey, Michael J. Marrone, Anthony Dandridge
  • Patent number: 5978125
    Abstract: Optical variable delay devices for providing variable true time delay to multiple optical beams simultaneously. A ladder-structured variable delay device comprises multiple basic building blocks stacked on top of each other resembling a ladder. Each basic building block has two polarization beamsplitters and a polarization rotator array arranged to form a trihedron; Controlling an array element of the polarization rotator array causes a beam passing through the array element either going up to a basic building block above it or reflect back towards a block below it. The beams going higher on the "ladder" experience longer optical path delay. An index-switched optical variable delay device comprises of many birefringent crystal segments connected with one another, with a polarization rotator array sandwiched between any two adjacent crystal segments.
    Type: Grant
    Filed: November 30, 1995
    Date of Patent: November 2, 1999
    Inventor: X. Steve Yao
  • Patent number: 5969850
    Abstract: A spatial light modulator has a modulating region which is capable of operating in two modes in the first clear mode, the region is continuously and substantially uniformly transmissive. In a second or barrier mode, the region can be switched to form parallax barrier comprising slits which are separated by continuous opaque regions. Such A modulator may be used in association with an image liquid crystal display to provide an autostereoscopic 3D display having a 3D mode which may track movement of an observer and a 2D mode in which full resolution of the LCD is used.
    Type: Grant
    Filed: September 25, 1997
    Date of Patent: October 19, 1999
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Jonathan Harrold, Graham John Woodgate
  • Patent number: 5892612
    Abstract: A switchable optical birefringent filter for polarized light incident thereon includes first and second retarder networks in optical series and a switch associated with at least one of the first and second retarder networks for selectively altering one of the polarization state and the angular orientation of the polarization state relative to the angular orientation of the second network, of light as it is received by the second network. In one operating mode, the filter produces a spectral filtration of light passing through the filter and in another mode transmits all light within a specified range of wavelengths without significant alteration.
    Type: Grant
    Filed: August 7, 1997
    Date of Patent: April 6, 1999
    Assignee: Cambridge Research & Instrumentation Inc.
    Inventors: Peter Miller, Carl Buhrer
  • Patent number: 5859728
    Abstract: A method and apparatus for modulating a light beam in an optical processing system is described. Preferably, an electrically-controlled polarizer unit and/or an analyzer unit are utilized in combination with a spatial light modulator and a controller. Preferably, the spatial light modulator comprises a pixelated birefringent medium such as a liquid crystal video display. The combination of the electrically controlled polarizer unit and analyzer unit make it simple and fast to reconfigure the modulation described by the Jones matrix of the spatial light modulator. A particular optical processing objective is provided to the controller. The controller performs calculations and supplies control signals to the polarizer unit, the analyzer unit, and the spatial light modulator in order to obtain the optical processing objective.
    Type: Grant
    Filed: October 24, 1994
    Date of Patent: January 12, 1999
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: Soutar Colin, Richard D. Juday
  • Patent number: 5815598
    Abstract: In an individual identification apparatus, a hologram 11 recorded on a card is irradiated with laser light to read out a fingerprint image of a specific person. A finger of an arbitrary person to be identified with the specific person is irradiated with laser light to obtain a fingerprint image. Thus obtained fingerprint images are jointly written in a first SLM. Then, the joint image is read out and Fourier transformed to obtain a Joint Fourier Transform image, which is then written in a second SLM. The Joint Fourier Transform image is then read out and Fourier transformed to obtain a pair of output correlation peaks. A photodetector detects the intensity of the output correlation peaks and outputs a signal indicative of the intensity. A threshold processor compares the value of the signal with a predetermined threshold value to positively or negatively identify the arbitrary person with the specific person.
    Type: Grant
    Filed: November 19, 1997
    Date of Patent: September 29, 1998
    Assignee: Hamamatsu Photonics K.K.
    Inventors: Tsutomu Hara, Yuji Kobayashi, Haruyoshi Toyoda
  • Patent number: 5801872
    Abstract: The invention provides a semiconductor optical modulation device which has low power dissipation, high extinction ratio and high speed response features. An n-type InP clad layer, an n.sup.- -type InAlAs-InAlGaAs composition inclination multiple layer, a p-type InP clad layer and a p.sup.+ -type InGaAs contact layer are layered on an n-type InP substrate. The layers are etched up to an intermediate location of the n-type clad layer to form a rib waveguide, and a positive electrode is formed on an upper portion of the rib waveguide. Further, a negative electrode is formed on the substrate.
    Type: Grant
    Filed: February 7, 1996
    Date of Patent: September 1, 1998
    Assignee: NEC Corporation
    Inventor: Masayoshi Tsuji
  • Patent number: 5796510
    Abstract: An ladder-structured variable delay device for providing variable true time delay to multiple optical beams simultaneously. The device comprises multiple basic units stacked on top of each other resembling a ladder. Each basic unit comprises a polarization sensitive corner reflector formed by two polarization beamsplitters and a polarization rotator array placed parallel to the hypotenuse of the corner reflector. Controlling an array element of the polarization rotator array causes an optical beam passing through the array element to either go up to a basic unit above it or reflect back towards output. The beams going higher on the "ladder" experience longer optical path delay. Finally, the ladder-structured variable device can be cascaded with another multi-channel delay device to form a new device which combines the advantages of the two individual devices. This programmable optic device has the properties of high packing density, low loss, easy fabrication, and virtually infinite bandwidth.
    Type: Grant
    Filed: April 7, 1997
    Date of Patent: August 18, 1998
    Inventor: X. Steve Yao
  • Patent number: 5793905
    Abstract: The method for switching optical radiations having orthogonal polarization includes the steps of inserting a linearly polarized wave into the input of a birefringent object (an optical waveguide or crystal) and feeding a small polarized small optical signal is also orthogonally into the object. The polarization vector of the linearly polarized pumping signal or of the optical signal is directed along an optical axis of the birefringent object or at a small angle to the optical axis. The pumping intensity is selected to be higher than the threshold value I.sub.p, which is proportional to a difference between the effective refractive indices of orthogonally polarized radiations and inversely proportional to a cubic nonlinear coefficient of the object. In addition, the intensity of the optical signal radiation is varied from zero to a maximum value of <0.1 I.sub.p.
    Type: Grant
    Filed: February 18, 1997
    Date of Patent: August 11, 1998
    Assignee: Maier Optical Research and Technologies GmbH
    Inventors: Alexandr Alexandrovich Maier, Konstantin Yurievich Sitarsky
  • Patent number: 5731890
    Abstract: A compound having nonlinear optical properties of the general formula:Ar.sup.1 CR.sup.1 .dbd.CR.sup.2 (Ar.sup.2 CR.sup.3 .dbd.CR.sup.4).sub.n Ar.sup.3 (I)wherein, n represents a whole number; R.sup.1, R.sup.1, R.sup.3 and R.sup.4 groups are independently selected from H, branched aliphatic, straight chain aliphatic, branched silane or straight chain silane; Ar.sup.1 and Ar.sup.3 are aromatic radicals having a substituent in at least one position adjacent to a site of attachment of the C.dbd.C double bond and having at least one electron withdrawing or electron donating substituent in at least one of the remaining positions; Ar.sup.2 is an aromatic radical having a substituent in at least one position adjacent to a site of attachment of the C.dbd.C double bond; with the proviso that the substituent in at least one position adjacent to the site of attachment of the C.dbd.C double bond and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 groups are sufficiently large to cause Ar.sup.1, Ar.sup.2 and Ar.sup.
    Type: Grant
    Filed: September 10, 1996
    Date of Patent: March 24, 1998
    Assignee: The University of Toledo
    Inventors: James E. Gano, Padmanabhan Sekher
  • Patent number: 5712721
    Abstract: A lens assembly (1) comprises a lens (2;10,11;20) the focal length of which may be changed by application of an electric or magnetic field. A switching means (4,15) provides a drive impulse to change the focal length of the lens (2;10,11;20). An integral power source (4,15) provides power for the switching means. A lens which can be switched between near and distance vision by the user is thereby provided.
    Type: Grant
    Filed: October 3, 1995
    Date of Patent: January 27, 1998
    Assignee: Technology Partnership, PLC
    Inventor: Timothy Andrew Large
  • Patent number: 5640267
    Abstract: An electro-optic material has first and second regions formed therein. The optic axes of the first and second regions are antiparallel and define a domain inversion pattern. The difference in refractive index between the first and second regions is a function of an electric field applied thereto. The difference in refractive index enables spatial light phase modulators and refractive optical devices having electrical control to be formed.
    Type: Grant
    Filed: March 1, 1995
    Date of Patent: June 17, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Paul May, Gillian Margaret Davis
  • Patent number: 5606453
    Abstract: Tunable optical parametric amplifiers and oscillators that are pumped by the light from a tunable laser source are disclosed. One possible embodiment uses a tunable solid-state laser pump and an OPA medium or nonlinear crystal, such as potassium titanyl phosphate KTP or barium borate BBO or lithium borate LBO. The second harmonic output from a tunable solid-state laser is also used to pump the OPA medium. A singly or doubly resonant cavity design is preferably used to reduce the oscillation threshold (i.e., the required pump beam power) of the OPO.
    Type: Grant
    Filed: April 20, 1993
    Date of Patent: February 25, 1997
    Assignee: Light Age, Inc.
    Inventors: John C. Walling, Jui T. Lin, Mahendrakumar G. Jani, Richard C. Powell, Donald F. Heller
  • Patent number: 5581010
    Abstract: A nonlinear optical material includes a noncentrosymmetric crystal of an anionic boron complex salt containing a cation and at least one organic ligand coordinated to a boron atom. The nonlinear optical crystal may consist of a compound having the formula A[BC.sub.2 ] where A is a monocation, B is boron, and C is the organic ligand, or a compound having the formula A[BC.sub.2 ].sub.2 where A is a dication, B is boron, and C is the organic ligand. The organic ligands may also be organic molecules having .alpha.-dihydroxy functionalities. Furthermore, the organic ligands may be selected from the group consisting of .alpha.-hydroxy carboxylic acids and 1,2-diols or from the group consisting of d-malic acid, d-lactic acid, d-tartaric acid, dimethyl-d-tartrate, diethyl-d-tartrate, l-malic acid, l-lactic acid, l-tartaric acid, dimethyl-l-tartrate, diethyl-l-tartrate, and ethylene glycol.
    Type: Grant
    Filed: July 22, 1994
    Date of Patent: December 3, 1996
    Assignee: Rockwell International Corporation
    Inventors: Patricia H. Cunningham, Leslie F. Warren, Jr., Henry O. Marcy, 5th, Mark J. Rosker
  • Patent number: 5555115
    Abstract: An optically addressed spatial light modulating system comprises a spatial light modulator using a liquid crystal material. A writing light irradiation device irradiates a writing light which records an image onto the spatial light modulator. A reading out light irradiation device irradiates a reading out light which is used to read out the recorded image from the spatial light modulator. A bias light irradiation device irradiates a bias light onto the spatial light modulator, and a bias light adjustment device changes at least one of the irradiation time and the light intensity of the bias light. A driving device supplies writing voltage signals to the spatial light modulator. The irradiation time of the write light and the irradiation time of the bias light overlap with the application time of the write voltage of the spatial light modulator for a predetermined amount of time for adjusting the sensitivity of the spatial light modulator.
    Type: Grant
    Filed: September 30, 1992
    Date of Patent: September 10, 1996
    Assignee: Seiko Instruments Inc.
    Inventors: Yasuyuki Mitsuoka, Tadao Iwaki, Nobuyuki Kasama
  • Patent number: 5546219
    Abstract: In the forward direction, the light from an input fiber is polarized and separated in a polarized light separating and combining element, the separated polarized light is rotated by a polarized light rotating element, dispersed according to wavelength by a wavelength dispersing element, rotated again by the polarized light rotating element, and is further rotated by a phase plate, thereby combining the polarized lights in the polarized light separating and combining element, so that only the light of a desired wavelength is coupled with the optical fiber. In the reverse direction, the light from the output fiber is not coupled with the input fiber, and hence the light propagation direction is defined in one direction in the disclosed optical circuit. A light transmission system and method using this optical circuit is also presented.
    Type: Grant
    Filed: March 3, 1995
    Date of Patent: August 13, 1996
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventor: Masanori Iida
  • Patent number: 5528393
    Abstract: This invention provides split-element liquid crystal polarization interference filters in wide-field, bandpass, cut-on, cut-off and notch filter embodiments. The split-element filters of this invention comprise a polarization interference stage defined by a pair of polarizers. Disposed within the stage are a center retarder, and first and a second split-element retarder, the split-element retarders having equal retardances and positioned in series with and on either side of the center retarder. The retarders can be liquid crystal variable retarders or can be fixed retarders used in combination with liquid crystal retarders. Double split-element filters in passive and tunable embodiments are provided comprising, within a polarization interference stage, a center retarder, an inside pair of split-element retarders and an outside pair of split-element retarders.
    Type: Grant
    Filed: July 12, 1994
    Date of Patent: June 18, 1996
    Assignee: Regents of the University of Colorado
    Inventors: Gary D. Sharp, Kristina M. Johnson
  • Patent number: 5485014
    Abstract: A multiple quantum well birefringent spatial light modulator has a substrate, multiple quantum well layers thereon, contacts for applying a biasing electric field across the multiple quantum well layers; and a component for varying the biasing electric field to produce birefringence in the multiple quantum well layer enhanced by the Stark effect and thereby effecting modulation of light exiting therefrom. The electric field may be varied directly by varying the voltage applied across the contacts or by providing a photodetector in series with the multiple quantum well layers and using a writing beam impinging on a photodetector to vary the field.
    Type: Grant
    Filed: December 30, 1993
    Date of Patent: January 16, 1996
    Assignee: The University of Connecticut
    Inventors: Faquir Jain, Siu K. Cheung
  • Patent number: 5440414
    Abstract: A method and apparatus for overcoming polarization induced signal fading in both heterodyne communication and interferometric sensing. An adjustable birefringent element in series with a linear-polarization beam splitter forms an elliptical-polarization beam splitter. The birefringent element controllably evolves the states of polarization of two input signals thereby controlling the power contribution of each signal onto the orthogonal axes used by the linear beam splitter. When the states of polarization are evolved such that there are equal signal to reference power ratios on the beam splitter axes, subsequent detectors generate a constant, optimum amplitude signal without the need for weighting or decision circuits.
    Type: Grant
    Filed: February 2, 1990
    Date of Patent: August 8, 1995
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventors: Alan D. Kersey, Michael J. Marrone
  • Patent number: 5436755
    Abstract: A raster output scanning system is disclosed which utilizes a single light source, an electro-optical device and a beam-splitter to generate two light beams in order to simultaneously scan two adjacent scan lines. Two different trains of pixel information are used to control the intensity of the laser light source and the degree of the polarization of the electro-optical device in order to modulate the two light beams with two separate trains of pixel information without using a modulating device. Each of the two light beams exiting the beam-splitter is modulated in accordance with one of the two trains of pixel information.
    Type: Grant
    Filed: January 10, 1994
    Date of Patent: July 25, 1995
    Assignee: Xerox Corporation
    Inventor: Jean-Michel Guerin
  • Patent number: 5414541
    Abstract: A liquid-crystal optical beam switch comprising: a first birefringent layer (14) which divides an input beam (24) into its two polarization components; a first segmented twisted nematic liquid-crystal polarization modulator (16), the segments (30,32) of which rotate one of the polarization beams by 90.degree.
    Type: Grant
    Filed: June 1, 1993
    Date of Patent: May 9, 1995
    Assignee: Bell Communications Research, Inc.
    Inventors: Jayantilal S. Patel, Yaron Silberberg
  • Patent number: 5381250
    Abstract: A family of optical switches employ dielectric film polarizing beam splitters and switchable electro-optic retarder to produce 2.times.2 optical switches which exhibit low crosstalk characteristics while switching unpolarized or linearly polarized collimated light. The switches all contain four port modules through which light enters and leaves the switch. The port modules utilize polarizing beam splitters to separate incoming light into two orthogonal linearly polarized components. The component beams are made parallel after which each passes through an electro-optic retarder. The retarders are electrically driven so as to selectively change the polarization of either one of the two component beams, thus making the polarizations the same. Other polarizing beam splitters are disposed to direct the component beams along one of two pairs of paths as determined by their common polarization.
    Type: Grant
    Filed: November 6, 1992
    Date of Patent: January 10, 1995
    Assignee: Displaytech, Inc.
    Inventor: Michael R. Meadows
  • Patent number: 5381278
    Abstract: A polarization conversion unit is disclosed. In the unit, a definitely polarized light emitted from a light source is divided into a pair of lights differing in polarized state and are caused to be incident on the optical components including the polarizing beam splitter. The plane of polarization of one of the paired polarized light is rotated to be coincident with the plane of polarization of the other light by the optical components, so that the paired lights with the same plane of polarization are caused to be separately emitted. The optical component has a plano-convex lens which has a positive power and which is arranged at an exit side where the paired lights are separately emitted. The lens has a focal point at a position further than the position of the surface to be illuminated.
    Type: Grant
    Filed: November 1, 1993
    Date of Patent: January 10, 1995
    Assignee: Canon Kabushiki Kaisha
    Inventors: Junko Shingaki, Hideaki Mitsutake, Kazumi Kimura
  • Patent number: 5351151
    Abstract: An optical filter device comprised of two parallel arrays of lenses. Each lens in the first array faces a lens in the second array to form a pixel. Lens pairs in a pixel are separated by the sum of their focal distances and include in their common focal surface a "smart" layer for modulating light passing through the focal surface. Preferred embodiments include car rear view mirrors, sunglasses, glasses for night driving, laser goggles, nuclear goggles, sun visors, sun shields, windshields, space suit helmet visors, optical instrument protection devices, window filters and energy conservation devices.
    Type: Grant
    Filed: February 1, 1993
    Date of Patent: September 27, 1994
    Inventor: George S. Levy
  • Patent number: 5327270
    Abstract: A polarizing beam splitter apparatus of a light valve image projection system includes a polarizing beam splitter commonly usable as a polarizer and an analyzer, and a quarter wave plate in combination. In the polarizing beam splitter apparatus, a quarter wave plate is arranged in a light path along which a light passes out from and passes back again to the polarizing beam splitter in such a manner that either a fast axis or a slow axis of the quarter wave plate is perpendicular to a plane containing both a first optical axis and a second optical axis of the polarizing beam splitter, so that the angular range of a light to be used can be increased. In the light valve image projection system, a light outputted from a light source is incident through a polarizing beam splitter apparatus to a light valve, and an effective component of the light reflected from the light valve is projected through the polarizing beam splitter apparatus and a projection lens on a projection screen.
    Type: Grant
    Filed: September 24, 1993
    Date of Patent: July 5, 1994
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventor: Yoshito Miyatake
  • Patent number: 5309530
    Abstract: A technique for reducing signal degradation and fading within a long optical transmission system by minimizing polarization dependent hole-burning ("PDHB") through the cyclic stressing of a birefringent optical fiber to modulate the SOP of an optical signal launched into the transmission system. This effectively reduces the degree of polarization of the launched optical signal, without degrading the noise and dispersion characteristics of the signal. The modulation frequency of the SOP is chosen to ensure that the launched signal does not remain at a particular SOP long enough to anisotropically saturate any optical amplifier employed within the transmission system, and give rise to PDHB.
    Type: Grant
    Filed: April 30, 1993
    Date of Patent: May 3, 1994
    Assignee: AT&T Bell Laboratories
    Inventors: Neal S. Bergano, Vincent J. Mazurczyk, Paul F. Wysocki
  • Patent number: 5305136
    Abstract: An optically bidirectional electrically controlled optical switch having reduced light loss includes an electro-optic crystal having one set of fast and slow optical axes and having at least two light paths for receiving light beams through the crystal, the crystal exhibiting electric field induced birefringence such that a light beam passing through the crystal along a light path and having a plane of polarization oriented in a first direction may have its plane of polarization switched from the first direction to a plane of polarization oriented in a second direction. Beam splitting polarizers are disposed at each end of the electro-optic crystal and optically aligned with the two light paths. The beam splitting polarizers split the optical beam into two light beams having planes of polarization oriented in the first and second directions when transmitting light to the two light paths and combine the two light beams into a single light beam when receiving light beams from the two light paths.
    Type: Grant
    Filed: March 31, 1992
    Date of Patent: April 19, 1994
    Assignee: Geo-Centers, Inc.
    Inventor: Malcolm C. Smith
  • Patent number: 5264951
    Abstract: There is provided an optical system for a spatial light modulator. The system comprises a light source for emitting an unpolarized light, a separator for separating a first linearly polarized light having a specified plane of polarization from the unpolarized light and polarizer for rotating the plane of polarization of the first linearly polarized light at a specified angle different from the specified angle to obtain a second linearly polarized light, wherein the second linearly polarized light is adopted as a reading light. Also provided is a method of photomodulation, comprising the steps of separating a light in the region of a specified wavelength from an unpolarized light, separating a first linearly polarized light having a specified plane of polarization from the light and obtaining a second linearly polarized light by rotating the plane of polarization of the first linearly polarized light at a specified angle.
    Type: Grant
    Filed: November 23, 1992
    Date of Patent: November 23, 1993
    Assignee: Victor Company of Japan, Ltd.
    Inventors: Itsuo Takanashi, Shintaro Nakagaki, Ichiro Negishi, Ryusaku Takahashi, Tetsuji Suzuki, Fujiko Tatsumi, Keiichi Maeno
  • Patent number: 5251058
    Abstract: In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate a scan line which can be turned on to have three levels of intensity. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together and combined into one beam without optical interference because the beams are polarized ninety degrees apart. The beam can have several levels of intensity and be used to create several levels of gray scale at the output.
    Type: Grant
    Filed: October 13, 1989
    Date of Patent: October 5, 1993
    Assignee: Xerox Corporation
    Inventor: Thomas D. MacArthur
  • Patent number: 5251057
    Abstract: In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate two consecutive scan lines. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together to within one scan line separation by a beam recombiner, which is a reversed beam splitter. The beams can be brought together to this close proximity without optical interference because the beams are plarized ninety degrees apart.
    Type: Grant
    Filed: October 13, 1989
    Date of Patent: October 5, 1993
    Assignee: Xerox Corporation
    Inventors: Jean-Michel Guerin, Melvin E. Swanberg
  • Patent number: 5240636
    Abstract: A haze-free light modulating polymer dispersed liquid crystal (PDLC) material is disclosed which comprises a polymer which is birefringent and possesses anisotropic optical properties similar to those of the dispersed liquid crystal such that the PDLC material in its transparent state exhibits a refractive index that is matched for all directions of incident light providing for an optically clear, scatter-free film for all angles of view. Electrooptic light shutters are possible from this material which are transparent in the field OFF-state and opaque in the field ON-state or vice versa, depending upon the liquid crystal phase structure and configuration of the light shutter device.
    Type: Grant
    Filed: March 30, 1992
    Date of Patent: August 31, 1993
    Assignee: Kent State University
    Inventors: Joseph W. Doane, John L. West
  • Patent number: 5164854
    Abstract: There is provided a polarization converter for producing a beam of linearly polarized light from a randomly polarized light. The randomly polarized light is separated into a first polarized light which is projected in a first predetermined direction and a second polarized light having a predetermined angular relationship with the first polarized light. The second polarized light is converted into a third polarized light a polarization of which is identical to that of the first polarized light. By providing a predetermined two-dimensional positional relationship between the first and third polarized lights, the beam of linearly polarized light is produced and advanced on the outside of the converter in a second predetermined direction.
    Type: Grant
    Filed: July 26, 1991
    Date of Patent: November 17, 1992
    Assignee: Victor Company of Japan, Ltd.
    Inventors: Itsuo Takanashi, Shintaro Nakagaki, Ichiro Negishi, Tetsuji Suzuki, Fujiko Tatsumi, Ryusaku Takahashi, Keiichi Maeno
  • Patent number: 5162944
    Abstract: An optical space switch includes a polarization controller, a beam splitter, a first reflection block and a second reflection block. The polarization controller has a first mode and a second mode. The polarization controller maintains the polarization of input light in the first mode and changes it by 90.degree. in the second mode. The first reflection block includes a quarter wave plate and a light path changing element. The input light from the polarization beam splitter is reflected by the first reflection block. During this time, the input light passes through the quarter wave plate twice. Thus, the polarization of the input light is changed by 90.degree.. Further, the light path of the input light is shifted by a predetermined distance by the light path changing element. The second reflection block has a quarter wave plate and a mirror. The second reflection block receives the input light from the polarization beam splitter, and returns it thereto.
    Type: Grant
    Filed: December 28, 1990
    Date of Patent: November 10, 1992
    Assignee: Fujitsu Limited
    Inventors: Tsuyoshi Yamamoto, Hiroyasu Itoh, Takakiyo Nakagami
  • Patent number: 5122895
    Abstract: An efficiency polarization converter of few optical components for converting a randomly polarized light into a single beam of linearly polarized light, comprises a first optical device receiving the random light and projecting two linearly polarized lights one projected in a first direction, another to a second optical device which changes the polarization plane thereof, the polarization changes light being directed by a third optical device to the first direction, thereby the two linearly polarized light are combined and aligned to have a common polarization to become the single beam linearly polarized light projected in the first direction. Typical first optical device is a polarization beam splitter, a typical second optical device is a quarterwave plate with a mirror, a halfwave plate or a Fresnel rhomb with a mirror, or a photomodulation material interposed between biased electrodes with a mirror, a typical third optical device is a polarization beam splitter, a prism or a mirror.
    Type: Grant
    Filed: December 4, 1990
    Date of Patent: June 16, 1992
    Assignee: Victor Company of Japan, Ltd.
    Inventors: Itsuo Takanashi, Shintaro Nakagaki, Ichiro Negishi, Tetsuji Suzuki, Fujiko Tatsumi, Ryusaku Takahashi, Keiichi Maeno
  • Patent number: 5107351
    Abstract: An image enhanced optical correlator system providing for optical preprocessing of an input image prior to processing thereof in an optical correlator. The optical preprocessing is provided to enhance the image and/or image related characteristics such that the probability of detection of prescribed targets therein in the optical correlator is increased. In the system, an input image beam is split into orthogonally polarized image inputs, processed to enhance targets therein, and then the algebraic result (addition and/or subtraction) thereof is processed through an optical correlator. Techniques are used in the feedback systems to enhance the output plane correlation signal detection by an adjustment in phase, spatial frequency filtering and/or threshold setting optimization.
    Type: Grant
    Filed: February 16, 1990
    Date of Patent: April 21, 1992
    Assignee: Grumman Aerospace Corporation
    Inventors: Kenneth G. Leib, Benjamin J. Pernick