Relief Illusion Patents (Class 359/478)
  • Patent number: 5886818
    Abstract: Image compositing apparatus and methodology for the creation, in a defined volume of three-dimensional space, of a composite organization of plural images/visual phenomena, including at least one projected real image, displayed in formats including (a) front-to-rear, (b) side-by-side and (c) overlapping and intersecting, adjacency. The apparatus incorporates different unique arrangements of visual sources, and optical elements including concave reflectors, beam splitters and image-forming/image-transmissive scrim/screen structures. In one important modification of the system, which does not necessarily require compositing, a projected real image is derived from an image-producing data stream containing three-dimensional image cues selected from the group consisting of shading, occlusion, perspective, motion parallax, size vs. depth, light (chroma value) vs. depth and definition vs. depth.
    Type: Grant
    Filed: November 2, 1994
    Date of Patent: March 23, 1999
    Assignee: Dimensional Media Associates
    Inventors: Susan Kasen Summer, Steve A. Welck, Burkhard Katz, Jon M. Dickinson, Pierre C. Van Rysselberghe
  • Patent number: 5883695
    Abstract: Method and apparatus for producing stereoscopic images for motion picture or TV using a single sensor or camera and a single lens. In carrying out the method of the invention, the camera lens is caused to rotate about an axis defined by the optical path of the incoming image rays. The apex of the cone is defined by the object being rendered. The base of the cone is defined by the image sensor portion of the camera and its circular path remains unchanged during an image rendering session. The lens of the camera, on the other hand, travels in a smaller circular path and the circumference of the path of travel of the lens is increased or decreased depending on the distance from the image to the lens and can change during the image rendering session. Apparatus comprises a frame which is driven by an electro mechanical drive mechanism for moving a camera support body through a conical path.
    Type: Grant
    Filed: September 19, 1997
    Date of Patent: March 16, 1999
    Inventor: Eddie Paul
  • Patent number: 5701210
    Abstract: An achromatic optical system for beam transformation is used for example with the optical head of an optical disk apparatus. This optical system is arranged in an optical path which is traversed by a beam emitted from a light source to reach a surface to be irradiated. This optical system includes a first prism arranged on the side of the light source and a second prism arranged on the side of the surface to be irradiated. The first and second prisms are constructed in such a manner that each of the prisms has a beam incident angle which is greater than its beam exit angle so as to expand the width of a beam passed therethrough and that with respect to a plurality of transmitted beams of different wavelengths the deviation angle of the beam passed through the optical system on the whole (the angle formed by the incident beam on the first prism and the emerging beam from the second prism) becomes the same for each other.
    Type: Grant
    Filed: October 27, 1994
    Date of Patent: December 23, 1997
    Assignee: Nikon Corporation
    Inventor: Katsura Ohtaki
  • Patent number: 5678910
    Abstract: The method and apparatus function to form three-dimensional imagery on plural screen surfaces (2) which are formed by changing planes of imagery. One or more projectors (4) project a plurality of images onto the screen surface from a common axis. The planes of imagery on the screens (2) which are projected by said one or more projectors (4), change at such a speed that, to the eye, the images appear simultaneously in three-dimensional form on said screen surfaces (2).
    Type: Grant
    Filed: November 30, 1995
    Date of Patent: October 21, 1997
    Assignee: Trutan Pty Limited
    Inventor: Donald Lewis Maunsell Martin
  • Patent number: 5589980
    Abstract: Optical viewing system for producing a simulated three dimensional image. The system includes electronic equipment for displaying an image on a first electronic display device. Additional electronic equipment is provided for displaying an image on at least one second display device. The at least one second electronic display device is a substantially transparent display device, whereby an observer can view through transparent areas of the second electronic display device. The first and second electronic display devices are located at different, predetermined locations along an optical viewing path such that the image displayed by the first electronic display device is projected through the second electronic display device. The first electronic display device includes an image projector and the second electronic display device includes a controllable pixel display spaced therefrom.
    Type: Grant
    Filed: June 23, 1994
    Date of Patent: December 31, 1996
    Inventors: Robert Bass, John Bass
  • Patent number: 5559632
    Abstract: Improved methods for 3-D motion picture, video or video game images with a one camera system. When a scene is photographed using this system to create 3-D, the scene must be lit so that the midground light intensity is approximately 50% greater than the intensity on the foreground and the background light intensity is approximately double that of the foreground with some subjects in the scene being backlit as well. The scene is photographed by a movable video or motion picture camera moving about the scene at a constant angular velocity in the range of 25-60 degrees per second. Additional cameras photograph the scene from fixed locations spaced approximately 120 degrees apart about the scene.
    Type: Grant
    Filed: September 7, 1993
    Date of Patent: September 24, 1996
    Inventors: John Lawrence, Linda S. Lukens
  • Patent number: 5556184
    Abstract: Imaginograph is an image on a screen which is mathematically generalized optical illusion to create psychological three dimensionality. These pictures are the would be "merged images in the brain" produced outside the brain. Rather than creating one picture for the left eye and another for the right, an Imaginograph is already the result of the analyzed signals. Using the property that when one is looking at a flat picture, the brain superimposes the two substantially same images in the left and right eyes and produces the same picture in the brain, Imaginographs are pictures which are formed by superimposing the left and right eye views at the same position as the object of interest in the view, keeping the images of the object of interest in the two pictures in register at all times. The left and right eye views and their projections can be generalized to obtain three dimensional views of non-Euclidean spaces.
    Type: Grant
    Filed: April 11, 1994
    Date of Patent: September 17, 1996
    Inventor: Rahim Nader-Esfahani
  • Patent number: 5543965
    Abstract: A lenticular autostereoscopic display includes a first layer, containing a composite image frame. The composite image frame is generated by creating a plurality of random dot image frames. Closely related pairs of image frames form a stereoscopic image when viewed stereoscopically. The plurality of random dot image frames are interlaced into a plurality of alternating vertical strips, and a lenticular material is placed over the composite image frame, allowing a viewer to perceive the stereoscopic image or images created by the interlaced random dot image frames.
    Type: Grant
    Filed: May 11, 1994
    Date of Patent: August 6, 1996
    Assignee: NVision Grafix, Inc.
    Inventors: Michael S. Bielinski, Paul G. Herber
  • Patent number: 5543964
    Abstract: An apparatus and method of creating depth images with different depth image scenes being projected at different viewer orientations. At each of the orientations a different perspective series is provided to the viewer. To provide the different depth scenes at the different orientations, different depth content image slices of different depth content scenes are interleaved behind lenticules of a lenticular faceplate. The interleaving of different depth content scenes on an imaging substrate is accomplished by writing to a print file depth images of the different depth content scenes in successive positions prior to driving the printer with the print file contents to record on the substrate. The substrate is then attached to the lenticular faceplate.
    Type: Grant
    Filed: December 28, 1993
    Date of Patent: August 6, 1996
    Assignee: Eastman Kodak Company
    Inventors: Roy Y. Taylor, William A. Doty, David J. Kroth, Roland R. Schindler
  • Patent number: 5529828
    Abstract: A method and structure for enhancing electromagnetic barrier properties including a substrate, a coating deposited upon the substrate, and a plurality of sets of patterns microembossed upon the surface of the coating layer for increasing the barrier properties of the structure. The plurality of sets of microembossed patterns each having a line density between about 100 and 50,000 lines per square centimeter.
    Type: Grant
    Filed: May 6, 1994
    Date of Patent: June 25, 1996
    Assignee: Flexcon Company, Inc.
    Inventors: Kirit Patel, John R. Pennace
  • Patent number: 5528425
    Abstract: An apparatus for providing optical illusion effects, which includes a first projection screen; an area from which persons may view the first projection screen; a stage area between the viewing area and the first projection screen; an illumination system for the stage area so that objects on the stage may be illuminated at a desired light level without directly illuminating the first screen; an inclined, partially silvered mirror between the viewing area and the stage area; a second projection screen positioned in a second plane at a first angle to the first plane, wherein the inclined mirror is positioned between the first and second planes; a first projector for projecting images on the first projection screen so that images on the first projection screen may be seen by viewers in the viewing area; a second projector for projecting images on the second projection screen so that images on the second projection screen are visible to the viewers by means of reflection from the mirror and appear to be located at
    Type: Grant
    Filed: October 6, 1993
    Date of Patent: June 18, 1996
    Assignee: Design Magic, Inc.
    Inventor: Robert T. Beaver
  • Patent number: 5519533
    Abstract: There is reproduced a three-dimensional image in which there is no dimness or no cross talk and which is light and high in resolution, by a three-dimensional information reproducing apparatus comprising a liquid crystal panel for displaying a discrete Fourier transform image, a light source array which is disposed to the rear of the liquid crystal panel and which emits parallel light, and a synchronous control device for switching, with time division, the discrete Fourier transform image that is displayed in the liquid crystal panel and also an angle of the parallel light that is emitted from the source light array.
    Type: Grant
    Filed: February 28, 1995
    Date of Patent: May 21, 1996
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Toshio Nomura, Masayuki Katagiri, Noritoshi Kako
  • Patent number: 5506703
    Abstract: A three-dimensional image display device which comprises a holographic plate having a plurality of holograms divided in correspondence with rotational angles, the holographic plate being exposed so that when light is irradiated, each of the holograms forms a point image at a different position in a depth direction of the holographic plate; a drive unit for rotating the holographic plate; a light irradiating unit including a plurality of light sources arranged substantially in a straight line so that the light sources are kept at substantially equal distances from the holographic plate, for irradiating the holographic plate with light from the light sources; and a controller for controlling the drive unit and lighting operations of the plurality of light sources of the light irradiating unit in accordance with a signal indicative of a three-dimensional image to be displayed so as to control lighting of a plurality of point images formed in a three-dimensional space, whereby a three-dimensional image can be obt
    Type: Grant
    Filed: February 16, 1994
    Date of Patent: April 9, 1996
    Assignee: Kabushiki Kaisha Komatsu Seisakusho
    Inventors: Toru Suzuki, Hideyuki Wakai, Manabu Ando, Kiyokazu Mizoguchi, Keiji Terada, Masato Moriya, Koji Shio
  • Patent number: 5488510
    Abstract: The optical viewing device for enhanced depth perception of images on a television screen comprises a hollow body of generally rectangular shape having a rectangular opening at the front, opaque sidewalls extending to the back of the device, and an open back. The sidewalls at the back opening are generally formed to provide a substantially light tight engagement with the face of a user. The front opening of the device is covered with one or two layers of mesh screen having the warp and weft diagonal to the rectangular opening at the front of the device. The optical viewing device is sized to locate the mesh screen three and one-half to four and one-half inches from the user's eyes for viewing a television screen at least eight feet from the user.
    Type: Grant
    Filed: July 26, 1994
    Date of Patent: January 30, 1996
    Inventor: Edward J. LeMay
  • Patent number: 5469295
    Abstract: A system and method of collecting and displaying images of isolated persons or objects in three dimensions; whereby isolated images of persons or objects (106) are collected on film or video by digitally removing the background and replacing it with black or collecting the image against a black background (107); and the isolated image (106) is projected with polarized light on to a partially reflective and transparent sheet polarizing screen (104) of an orthogonal polarization sense to that of the projected light. The screen stops and reflects the image (105), but the screen is partially-transparent to light polarized parallel to its polarization sense making a real three dimensional physical object (103B) behind the screen visible from a position in front of the screen. The isolated image (105) on the screen (104) in the presence of real physical three dimensional objects (103A) and (103B) appears to be three dimensional.
    Type: Grant
    Filed: January 18, 1994
    Date of Patent: November 21, 1995
    Inventor: Douglas Burke
  • Patent number: 5418632
    Abstract: A three dimensional display having a rotating screen, preferably helical in shape, a light source providing a beam of light and a holographic pattern deflecting the beam of light to predetermined points on the screen. The light is modulated, preferably by the holographic pattern. The holographic pattern rotates with the same angular velocity as the screen. The holographic pattern comprises a plurality of concentric circles, each of the circles comprising a plurality of cells, each of the cells representing a point on the screen.
    Type: Grant
    Filed: January 21, 1994
    Date of Patent: May 23, 1995
    Assignee: Texas Instruments Incorporated
    Inventor: Douglas W. Anderson
  • Patent number: 5373863
    Abstract: The present invention is directed to a portable mirrored camouflage blind that incorporates a plurality of two-way mirrored panels positioned relative to each other side by side along a longitudinal edge, and flexible hinge means for flexibly connecting each of the plurality of two-way mirrored panels with an adjacent two-way mirrored panel whereby the plurality of two-way mirrored panels with the flexible hinge means form an accordion-like structure. Each of the plurality of two-way mirrored panels is optically constructed to produce undistorted reflections of objects located at near and far distances on an outer side of the plurality of two-way mirrored panels.
    Type: Grant
    Filed: December 29, 1992
    Date of Patent: December 20, 1994
    Inventor: Ricci Prizio
  • Patent number: 5371627
    Abstract: A random dot stereogram is formed using a novel method from relatively fine pixels. The "dots" of the stereogram are formed from the pixels in diverse shapes and sizes and are measurably more random in particular respects than dots used in the prior art. The dots are constructed in such a manner that they have a greater range of pixel counts per dot and tend to have more sides and a greater range of size counts than do prior art dots. An apparent three-dimensional image is formed on the dot background by shifting groups of dots, with the amount of the shift determining the apparent height of the group of dots. Superior resolution in the apparent height of the dot groups is obtained by assigning the quantum of movement to be significantly less than the size of the dots. The combination of the increased randomization of the dots and the reduction of the quantum of movement (for example, to 1/300 inch) produces a resolution which was not available using prior art methods.
    Type: Grant
    Filed: October 23, 1992
    Date of Patent: December 6, 1994
    Assignee: N.E. Thing Enterprises, Inc.
    Inventors: Thomas J. Baccei, Robert Salitsky
  • Patent number: 5329323
    Abstract: Systems and methods for producing the sensation of 3-dimensional viewing by projecting and displaying a foreground image and a background image onto separate projection screens positioned on a single viewing axis are disclosed. The images are viewed simultaneously and appear as a single image having depth characteristics. The foreground image screen and the background image screen are provided with image transmission, reflection, and absorption characteristics which allow for simultaneous viewing of more than one screen without image "bleed" or excessive loss of image intensity.
    Type: Grant
    Filed: March 25, 1992
    Date of Patent: July 12, 1994
    Inventor: Kevin Biles
  • Patent number: 5310576
    Abstract: A method and structure for enhancing electromagnetic barrier properties including a substrate, a metallic layer deposited upon the substrate by vacuum metalization, and a plurality of sets of patterns microembossed upon the surface of the metallic layer for increasing the barrier properties of the structure. The plurality of sets of microembossed patterns each have a line density between about 100 and 50,000 lines per square centimeter.
    Type: Grant
    Filed: November 9, 1992
    Date of Patent: May 10, 1994
    Assignee: FLEXcon Company, Inc.
    Inventors: Kirit Patel, John R. Pennace
  • Patent number: 5299058
    Abstract: A method of reproducing a mirage-like phenomenon which comprises forming a structure comprising at least two see-through phases wherein the density of a lower phase in contact with an upper phase is larger than that of the upper phase, the density ratio (A) therebetween is 1<A<50 and the interface between the lower phase and the upper phase has an even or curved surface.
    Type: Grant
    Filed: April 20, 1992
    Date of Patent: March 29, 1994
    Assignee: Nippon Carbide Kogyo Kabushiki Kaisha
    Inventors: Tetsu Tanaka, Isamu Amemiya, Chikanobu Tomikawa, Koji Aoki
  • Patent number: 5291330
    Abstract: A system for enhancing the resolution of an image comprising a plurality of phase affecting light transmitting objects, preferably plates, disposed in a stack in the light path of the light energy defining an image, each plate having a thickness and being spaced a distance apart from others of the plates. Preferably, a source of radiant energy is provided for irradiating the plates and spaces between the plates in the stack and optionally the image itself to enhance resolution further by creating standing waves that interfere with the light in the light path defining the image. The plates are preferably edge illuminated, and the radiant energy may be visible light, ultraviolet energy or infrared energy, individually or intermixed. The system has application both for enhancing existing images as well as enhancing images during the image storage process.
    Type: Grant
    Filed: November 3, 1989
    Date of Patent: March 1, 1994
    Inventor: Joseph Daniels
  • Patent number: 5257130
    Abstract: An apparatus and method for creating real image illusions utilizes a partially transparent scrim positioned between the real image and an optical system which produces the real image from a corresponding real object. When the scrim is illuminated by a light source or projector in front of and at an oblique angle to the scrim, the scrim forms a seemingly solid and non-transparent surface that conceals the optical system from view by an observer. The scrim also protects the optical system from damage and other vandalism, yet it does not distort or interfere with the light rays passing through the scrim to form the real image. The scrim also avoids distracting surface reflections, ghosting and other highlights.
    Type: Grant
    Filed: January 30, 1992
    Date of Patent: October 26, 1993
    Assignee: The Walt Disney Company
    Inventor: Marshall M. Monroe
  • Patent number: 5220452
    Abstract: There is disclosed a method and system for controlling the optics of a coherent light source impacting a three dimensional defined volume. The system uses a scanner to time and spatially position the coherent light. The divergent light beam output of the scanner is then placed through positive and negative lenses to narrow the beam waist while also increasing the divergence angle of the beam. Provision is made to abate the divergence angle so that the light, as it impacts the defined volume, will not continue to diverge, creating a skewed image within the volume.
    Type: Grant
    Filed: August 7, 1991
    Date of Patent: June 15, 1993
    Assignee: Texas Instruments Incorporated
    Inventor: Douglas W. Anderson
  • Patent number: 5211997
    Abstract: A structure exhibiting enhanced barrier properties is disclosed and which comprises:a substrate,a metallic coating formed by vaporization and condensation upon said substrate, said metallic coating having a thickness of about 400A, anda plurality of sets of embossed patterns upon said coating, said plurality of sets of embossed patterns each having a line density between 100 and 50,000 lines per square centimeter, and method of making the structure.
    Type: Grant
    Filed: January 29, 1990
    Date of Patent: May 18, 1993
    Inventors: Kirit Patel, John R. Pennace
  • Patent number: 5181028
    Abstract: An integrated attitude director indicator and horizontal situation indicator is disclosed that utilizes stereopsis to combine information that normally requires two display surfaces onto a single electronic display. One embodiment of the display comprises left and right eye versions alternately presented on the display in synchronism with alternate eye shuttered lenses worn by the viewer. The viewer has an instantaneous sense of the real world direction from his aircraft as apparently suspended within a spherical grid. The integrated display provides a presentation somewhat similar to existing flat screen separate instruments with an aircraft symbol lying at the center of the sphere with roll, pitch and heading scales displayed on this sphere. The sphere itself has one color such as blue above the horizon line and a different color such as brown below the horizon line.
    Type: Grant
    Filed: June 20, 1990
    Date of Patent: January 19, 1993
    Assignee: Rockwell International Corporation
    Inventors: Tom G. Sharpe, C. James Styers, James M. Suiter
  • Patent number: 5172266
    Abstract: A three dimensional display system is shown wherein a scanned light beam is displayed upon a continuously rotating display member rotating about a fixed axis. A first embodiment provides that the display member be comprised of a pair of intersecting display surfaces. In a further version the display member is fixedly positioned in a spherical enclosure which is rotatable in two different directions. In a second embodiment, the display member is formed by a bundle of fiber optic elements extending from an image projector to a viewing surface. The optical fiber bundle can be formed so that the image receiving portion has a smaller cross section than the image transmitting portion. In a third embodiment, the angle formed between the display member and the axis about which it rotates is adjusted, on or off line, by changing the length of an adjustable rod secured to the display member and a member rotating with the display member.
    Type: Grant
    Filed: July 18, 1991
    Date of Patent: December 15, 1992
    Assignee: Texas Instruments Incorporated
    Inventors: Felix Garcia, Rodney D. Williams
  • Patent number: 5161052
    Abstract: A stereoscopic tandem scanning reflected light confocal microscope employs longitudinal and transverse chromatic aberration in conjunction with color dispersion prisms in a binocular eyepiece assembly to provide a three dimensional vertical view through a specimen.
    Type: Grant
    Filed: March 29, 1991
    Date of Patent: November 3, 1992
    Assignee: Tandem Scanning Corporation
    Inventor: James D. Hill
  • Patent number: 5157546
    Abstract: A system wherein the observer can be positioned at the interior of a three dimensional display and observe the display looking outwardly therefrom. In accordance with a first embodiment of the invention, the rotating disk of the prior art is made sufficiently large and at sufficient angle, preferably 45 degrees with respect to the shaft rotating the disk, so that the observer or a camera can be located in a conical portion of the cylinder swept out by the disk wherein the disk does not travel. In accordance with a second embodiment of the invention, the rotating shaft onto which the disk is anchored is a hollow, transparent cylinder and is sufficiently large to retain a viewer or a camera within the cylinder. In this way, the observer can rotate 360 degrees within the cylinder to view the entire display looking outwardly from the interior thereof.
    Type: Grant
    Filed: December 19, 1990
    Date of Patent: October 20, 1992
    Assignee: Texas Instruments Incorporated
    Inventors: Rodney D. Williams, Felix Garcia, Jr.
  • Patent number: 5144344
    Abstract: The present invention relates to a pair of spectacles for stereoscopic pictures based upon the principle of the Pulfrich effect. The direction in which a moving object is moving in a picture or the moving direction of a video camera is marked on the spectacles for stereoscopic pictures to obtain a correct stereoscopic image, so that the viewer can easily and readily determine which of a darker lens or a lighter lens is applied to which eye. According to the invention, the connecting portions between the front frame and the temples of the spectacles are formed as a pair of hinges which protrude from the inside front frame and are spaced apart from each other so that a space therebetween receives the hinges of a pair of standard glasses worn by a viewer to support the stereoscopic spectacles on the standard glasses with great stability. This also enables the stereoscopic spectacles to be reduced in size so that they may be worn more stably by those who do not wear vision correcting glasses.
    Type: Grant
    Filed: May 24, 1990
    Date of Patent: September 1, 1992
    Assignee: Sony Corporation
    Inventors: Katsumasa Takahashi, Takuya Nakamaru, Osamu Iino
  • Patent number: 5144482
    Abstract: A method and apparatus for viewing two dimensional images with a three dimensional effect utilizes a stack of closely spaced, thin plates, producing a multiple interferometer effect via inter and intra plate reflections between the plates. A conventional two dimensional image, such as a print or a back-lighted transparency or a video screen may be viewed through the stack of plates, so as to give an appearance and attributes of three dimensions, via the multiple interferometer effect. In a second embodiment, dedicated images may be produced by photographing or videotaping or otherwise recording images through the stack of plates. When such a dedicated image is later viewed through the stack of plates, a further enhanced three dimensional effect is observed. In preferred embodiments the stack of plates include about 10 to 100 thin plates, in closely and evenly spaced relationship.
    Type: Grant
    Filed: May 13, 1991
    Date of Patent: September 1, 1992
    Inventor: Dennis R. Gould
  • Patent number: 5105306
    Abstract: A visual effect comprising an array of sections formed in a surface. The sections have a facet and a reflective medium is formed on the facets. The facets are sloped in a predetermined way to correspond to sections in a real or imagined three-dimensional scene to create an image that simulates the scene.
    Type: Grant
    Filed: January 18, 1989
    Date of Patent: April 14, 1992
    Inventor: John J. Ohala
  • Patent number: 5082350
    Abstract: A three dimensional display system is shown wherein a scanned light beam is displayed upon a continuously rotating display member rotating about a fixed axis. A first embodiment provides that the display member be comprised of a pair of intersecting display surfaces. In further version the display member is fixedly positioned in a spherical enclosure which is rotatable in two different directions. In a second embodiment, the display member is formed by a bundle of fiber optic elements extending from an image projector to a viewing surface. The optical fiber bundle can be formed so that the image receiving portion has a smaller cross section than the image transmitting portion. In a third embodiment, the angle formed between the display member and the axis about which it rotates is adjusted, on or off line, by changing the length of an adjustable rod secured to the display member and a member rotating with the display member.
    Type: Grant
    Filed: September 19, 1989
    Date of Patent: January 21, 1992
    Assignee: Texas Instruments Incorporated
    Inventors: Felix Garcia, Rodney D. Williams
  • Patent number: 5042909
    Abstract: A three dimensional display wherein a scanned light beam is displayed upon a rotating display member rotating about a fixed axis for receiving and displaying the scanned light beam on a first surface thereof, fixed points in the display impinging upon the display member to display a harmonic motion along an axis passing through the scanned light beam in response to rotation of the display means. In accordance with a second embodiment of the invention, the display member is translucent and a second scanned light beam is displayed upon an opposing surface of the display member for receiving and displaying the second scanned light beam on the opposing surface thereof to display a harmonic motion along an axis passing through the second scanned light beam in response to rotation of the display means.
    Type: Grant
    Filed: September 17, 1990
    Date of Patent: August 27, 1991
    Assignee: Texas Instruments Incorporated
    Inventors: Felix Garcia, Jr., Rodney D. Williams