Utilizing Radiant Energy Patents (Class 219/85.12)
  • Patent number: 10436688
    Abstract: Heating arrangement for a materials testing device, the materials testing device comprising at least one surface measurement probe adapted to be brought into contact with a surface of a sample, the heating arrangement comprising a probe heater comprising: an infrared emitting element adapted to emit infrared radiation; a reflector having a reflective surface arranged to direct said infrared radiation towards a distal end of said surface measurement probe. According to the invention, the reflector comprises a first focal point and a second focal point, the infrared emitting element being situated substantially at said first focal point.
    Type: Grant
    Filed: November 2, 2015
    Date of Patent: October 8, 2019
    Assignee: ANTON PAAR TRITEC SA
    Inventors: Bertrand Bellaton, Marcello Conte
  • Patent number: 10337913
    Abstract: An optoelectronic module, intended to provide a conversion of an electrical signal from an electronic board into an optical signal propagated in free space or vice versa, includes the following stack: an electronic board, intended to act as an interface with an electronic application board; an electronic control component suitable for controlling an optoelectronic component, the electronic component being attached directly onto the electronic board and electrically connected to the electronic circuit; an optoelectronic component suitable for transmitting or receiving a light signal via its upper surface, the optoelectronic component being attached directly on the top of the electronic control component and electrically connected to the electronic component; an optical device suitable for transmitting an optical signal; an optical device support, the support being attached, preferably by gluing or brazing, directly onto the electronic board so as to ensure the mechanical alignment between the optical device an
    Type: Grant
    Filed: June 2, 2016
    Date of Patent: July 2, 2019
    Assignee: RADIALL
    Inventors: Vincent Foucal, Christian Claudepierre, Mathias Pez, Laurence Pujol, François Quentel
  • Patent number: 10265740
    Abstract: A method of cleaning solder from the jaws of a solder ball test device including the steps of heating a gas to a temperature above the melting temperature of the solder and directing the heated has over the jaws of a solder ball test device to remove solder from the jaws, and an apparatus for carrying out the method.
    Type: Grant
    Filed: July 17, 2015
    Date of Patent: April 23, 2019
    Assignee: XYZTEC BV
    Inventor: Robert Sykes
  • Patent number: 10016842
    Abstract: An method and apparatus for carrying out precise laser cutting on a ribbon sheet positioned in a laser cutting station includes providing a laser cutting station that comprises a conveyor for advancing the ribbon sheet, a cutting head movable along both a longitudinal and a transverse axis in relation to the station, a vision system also movable along the same axes, and a command and control center with associated software that commands the movements of the cutting head and of the vision system, wherein the command and control center is provided with the coordinates of a CAD/CAM drawing corresponding to the ribbon sheet to be processed.
    Type: Grant
    Filed: June 16, 2016
    Date of Patent: July 10, 2018
    Inventor: Andrea Dallan
  • Patent number: 9310531
    Abstract: A member having an arbitrary shape having a closed curve can be easily subjected to laser processing within a short time. A lens and a laser processing apparatus equipped with the lens are for cutting a material to be cut into a member having an arbitrary shape having a closed curve and include a convex cylindrical lens which is molded to have a closed path so that a line that connects vertices of a cylindrical surface of the convex cylindrical lens has the same form as the arbitrary shape having the closed curve.
    Type: Grant
    Filed: May 9, 2012
    Date of Patent: April 12, 2016
    Assignee: V-TECHNOLOGY CO., LTD.
    Inventors: Kouichi Kajiyama, Makoto Hatanaka
  • Patent number: 8867113
    Abstract: A laser processing device includes a laser light source, a spatial light modulator, a control section, and a condensing optical system. The spatial light modulator, presents a hologram for modulating the phase of the laser light in each of a plurality of two-dimensionally arrayed pixels, and outputs the phase-modulated laser light. The control section causes a part of the phase-modulated laser light (incident light) to be condensed at a condensing position in a processing region as a laser light (contribution light) having a constant energy not less than a predetermined threshold X. The control section causes a laser light (unnecessary light) other than the contribution light condensed to the condensing position existing in the processing region to be dispersed and condensed at a condensing position existing in a non-processing region as a plurality of laser lights (non-contribution lights) having an energy less than the predetermined threshold.
    Type: Grant
    Filed: August 24, 2009
    Date of Patent: October 21, 2014
    Assignee: Hamamatsu Photonics K.K.
    Inventors: Naoya Matsumoto, Takashi Inoue, Norihiro Fukuchi, Haruyasu Ito
  • Patent number: 8866041
    Abstract: A manufacturing method of laser diode unit of the present invention includes steps: placing a laser diode on top of a solder member formed on a mounting surface of a submount, applying a pressing load to the laser diode and pressing the laser diode against the solder member, next, melting the solder member by heating the solder member at a temperature higher than a melting point of the solder member while the pressing load is being applied, and thereafter, bonding the laser diode to the submount by cooling and solidifying the solder member, thereafter, removing the pressing load, and softening the solidified solder member by heating the solder member at a temperature lower than the melting point of the solder member after the pressing load has been removed, and thereafter cooling and re-solidifying the solder member.
    Type: Grant
    Filed: April 12, 2012
    Date of Patent: October 21, 2014
    Assignees: TDK Corporation, Rohm Co., Ltd, SAE Magnetics (H.K.) Ltd.
    Inventors: Koji Shimazawa, Osamu Shindo, Yoshihiro Tsuchiya, Yasuhiro Ito, Kenji Sakai
  • Patent number: 8803023
    Abstract: A process is provided for scam welding advanced high strength steel sheets together. Respective end portions of first and second advanced high strength steel sheets are placed in overlapping contact with one another, and subjected to first and second weld passes. In the first weld pass, a seam welder including weld electrodes operate at a first-pass applied current and a first-pass pressure and are moved relative to the overlapping end portions at a first-pass carriage speed to establish a weld seam containing a weld nugget with a martensite phase. In the second weld pass, the weld electrodes operate at a second-pass applied current and a second-pass pressure and move relative to the weld seam at a second-pass carriage speed selected to fuse microcracks, lap openings, and porosity in the seam, relieve the residual stress in the joint, and temper the martensite phase of the weld nugget, and thereby form a weld joint.
    Type: Grant
    Filed: November 3, 2008
    Date of Patent: August 12, 2014
    Assignee: ISG Technologies
    Inventor: Soumitra V. Agashe
  • Publication number: 20140211384
    Abstract: A method of manufacturing an electronic device in which an inner space for housing a gyro element is formed between a base and a lid and the base and the lid are bonded includes bonding the base and the lid in which a groove is provided on a surface to be bonded with the base so that the inner space communicates with the outside by not bonding the inner surface of the groove to the base and to position the groove around a concave portion provided on a side surface of the base, and closing a communication portion by irradiating a laser beam to the lid in the communication portion.
    Type: Application
    Filed: January 27, 2014
    Publication date: July 31, 2014
    Applicant: Seiko Epson Corporation
    Inventors: Shinya AOKI, Juichiro MATSUZAWA, Osamu KAWAUCHI, Masaru MIKAMI
  • Patent number: 8716630
    Abstract: A visually seamless method of joining a first piece of metal and a second piece of metal is described. The first piece of metal is placed in contact with an edge of the second piece of metal. In some embodiments, the edge includes a sacrificial lip. The first piece of metal forming a junction area with the edge of the second piece of metal, applying a forging force to the first piece of metal, the forging force having an effect of creating an extremely tight fit up between the first and the second pieces of metal, welding the first and the second pieces to form an assembly and forming a cosmetically enhancing protective layer on the surface of the assembly, the protective layer obscuring any visible artifacts on the surface of the assembly, the obscured visible artifacts including any discoloration or discontinuity created by the laser welding.
    Type: Grant
    Filed: September 13, 2012
    Date of Patent: May 6, 2014
    Assignee: Apple Inc.
    Inventors: Carlo Catalano, Derrick Jue, Brian Miehm, Takahiro Oshima, Masashige Tatebe
  • Patent number: 8704137
    Abstract: This invention introduces the welding technology of an electrical connector and its welding device. The welding device comprises of a base frame, IR lamp that can emit infrared rays, and convex lens used to collect infrared rays. The lamp and lens are set in the base frame, with the convex lens in front, which collects all infrared rays from the lamp and irradiates them to the solder paste, allowing for fast heating. The melted solder paste forms defect-free welding spots with sound electrics performance and low energy consumption, thus saving energy. This invention of welding device is used for the welding when electrical connector is assembled, solder paste is put and the connector is fixed in the conveying belt. The electrical connector goes through the heating zone in welding device, which enables the automatic welding of each cored wire in the electrical connector and wire connecting terminal. The welding is fast and the production can be continuous free of any tack welding.
    Type: Grant
    Filed: September 24, 2008
    Date of Patent: April 22, 2014
    Inventor: Ching-Jen Hsu
  • Publication number: 20130284707
    Abstract: An apparatus for mounting and removing a component includes: a light source configured to radiate light toward a component supported by solder; a light sensor configured to sense displacement of the component; and a member mounted on the component, the member including a hole in a portion to be irradiated with the light of the light source.
    Type: Application
    Filed: January 30, 2013
    Publication date: October 31, 2013
    Applicant: FUJITSU LIMITED
    Inventors: Yasuyuki KUSAKABE, Tooru Harada
  • Patent number: 8324522
    Abstract: Provided is an apparatus for performing a reflow process of a solder ball provided to a semiconductor chip. The reflow apparatus may include a coil, a support member and a moving member. The coil may receive a current from a power supply to heat the solder ball using an induced heating method. The support member may be disposed on the front or the rear of the coil and may support a printed circuit board on which a semiconductor chip is mounted. The moving member may move the printed circuit board so that the printed circuit object passes through an internal space surrounded by the coil.
    Type: Grant
    Filed: December 2, 2009
    Date of Patent: December 4, 2012
    Assignee: Samsung Electronics Co., Ltd.
    Inventors: Minill Kim, Kwang Yong Lee, Jonggi Lee, Ji-Seok Hong
  • Patent number: 7649152
    Abstract: The present invention provides a solder ball bonding method and a solder ball bonding apparatus, which can enhance efficiency of bonding processing and in which plural electrodes formed on objects to be bonded are bonded to each other by melting a solder ball. In the present invention, the solder balls are picked up by a pick-up nozzle having a plurality of pick-up openings corresponding to electrode areas on the objects to be bonded and the solder balls are conveyed on the electrode areas. A laser radiating unit disposed independently above the pick-up nozzle is shifted along an arrangement direction of the pick-up openings and a laser beam from the laser radiating unit is irradiated onto the solder ball through a transparent member of the pick-up nozzle and through the pick-up opening of the pick-up nozzle, thereby melting the solder ball on the electrode area.
    Type: Grant
    Filed: September 23, 2005
    Date of Patent: January 19, 2010
    Assignees: TDK Corporation, SAE Magnetics (H.K.) Ltd.
    Inventors: Osamu Shindo, Toru Mizuno, Satoshi Yamaguchi
  • Publication number: 20090289039
    Abstract: A circuit board and components provided thereupon are held by and between lower and upper palettes. The upper palette has protecting portions that are provided above and opposed to the components. The shielding components prevent light beams irradiated by a preheating light source from directly reaching the components made of colored synthetic resin. Meanwhile, the upper palette has openings that are opposed to the circuit board except for the components protected by the protecting portions members. The light beams from the light source travel through the openings and applied to the circuit board. Openings are formed so as to be opposed to terminals that are soldered on and connected to the circuit board. Inner surfaces of the openings are made of light-reflecting material that reflects downward the light beams from the light source.
    Type: Application
    Filed: May 11, 2009
    Publication date: November 26, 2009
    Applicant: Yazaki Corporation
    Inventors: Kazuhide Takahashi, Kimitoshi Makino, Takafumi Toda
  • Publication number: 20090223937
    Abstract: A wire bonding apparatus includes a processing block, a bond head assembly and an infrared radiation source for selectively heating the bond pad areas of one or more semiconductor dies and/or bonding sites on a substrate. Methods for forming wire bonds using selective heating of the bond pad areas of one or more semiconductor dies and/or bonding sites on the substrate are also disclosed.
    Type: Application
    Filed: April 4, 2008
    Publication date: September 10, 2009
    Applicant: MICRON TECHNOLOGY, INC.
    Inventors: Low Peng Wang, Mitchell Ong, Lee Choon Kuan
  • Patent number: 7326892
    Abstract: A process for heating a powder material by microwave radiation so that heating of the powder material is selective and sufficient to cause complete melting of the particles. The process entails providing a mass of powder comprising a quantity of filler particles of a metallic composition, and subjecting the mass to microwave radiation so that the filler particles within the mass couple with the microwave radiation and are completely melted. According to one aspect, the mass further contains at least one constituent that is more highly susceptible to microwave radiation than the filler particles, and the filler particles are melted as a result of heating by microwave radiation and thermal contact with the at least one constituent. According to another aspect, the powder mass is thermally pretreated to induce an irreversible increase in its dielectric loss factor prior to melting by microwave irradiation.
    Type: Grant
    Filed: September 21, 2006
    Date of Patent: February 5, 2008
    Assignee: General Electric Company
    Inventors: Laurent Cretegny, David Edwin Budinger, Vasile Bogdan Neculaes, Holly Sue Shulman, Morgana Lynn Fall, Shawn Michael Allan
  • Patent number: 7189274
    Abstract: An exhaust gas filter for cleaning an exhaust gas of an internal combustion engine includes at least one strip-shaped filter layer made of a material through which a fluid can at least partly flow. The filter layer has a length in a longitudinal direction and a width in a transverse direction. The filter layer has a metallic reinforcing region at least in a partial region. The metallic reinforcing region has a width and a length. The width of the reinforcing region is less than the width of the filter layer and/or the length of the reinforcing region is less than the length of the filter layer. A method for producing a filter layer for an exhaust gas filter is also provided.
    Type: Grant
    Filed: February 2, 2005
    Date of Patent: March 13, 2007
    Assignee: Emitec Gesellschaft für Emissionstechnologie mbH
    Inventors: Rolf Brück, Jan Hodgson, Markus Mengelberg
  • Patent number: 7164097
    Abstract: Provided are a solder ball bonding method and a solder ball bonding device for performing bonding of a plurality of electrode portions formed on objects to be bonded by melting solder balls. The solder balls are suctioned by using a plurality of suction nozzles that follow the electrode portions of the objects to be bonded, and conveyed onto the electrode portions. A laser irradiation portion that is positioned above the suction nozzles is then moved in a direction along which the suction nozzles are arranged, while the solder balls are irradiated with laser light passing through suction openings of the suction nozzles by using the laser irradiation portion. Accordingly, it is possible to melt the plurality of solder balls on the electrode portions by using only a single laser irradiation portion.
    Type: Grant
    Filed: September 9, 2004
    Date of Patent: January 16, 2007
    Assignee: TDK Corporation
    Inventors: Osamu Shindo, Toru Mizuno, Youichi Andoh, Satoshi Yamaguchi
  • Patent number: 6917010
    Abstract: The present invention includes a method for brazing of two objects or heat treatment of one object. First, object or objects to be treated are selected and initial conditions establishing a relative geometry and material characteristics are determined. Then, a first design of an optical system for directing heat energy onto the object or objects is determined. The initial conditions and first design of the optical system are then input into a optical ray-tracing computer program. The program is then run to produce a representative output of the heat energy input distribution to the object or objects. The geometry of the object or objects, material characteristics, and optical system design are then adjusted until an desired heat input is determined.
    Type: Grant
    Filed: April 29, 2003
    Date of Patent: July 12, 2005
    Assignee: The Regents of the University of California
    Inventors: John O. Milewski, Vivek R. Dave′, Dane Christensen, Robert W. Carpenter, II
  • Patent number: 6857550
    Abstract: An optically baffled heating station for joining wire connections by using a solder sleeve includes: an outer housing; a reflection block where said reflection block includes a reflection chamber where the reflection chamber forms the shape of two overlapping ellipses where the ellipses intersect at one respective focal point of each ellipsis and the opposing non-intersecting focal points are separated by about a 90° angle; two heating elements within a heating element block where the two heating elements extend beyond the heating element block and protrude into the reflection pockets of the reflection chamber. A slot extends between the two heating elements through the reflection block and the heating element block. The closed end of the slot includes a target area where the shrinking of the sleeve occurs. The target area receives the reflected light and minimizes the reflection of light toward the open end of the slot.
    Type: Grant
    Filed: January 15, 2003
    Date of Patent: February 22, 2005
    Assignee: The Boeing Company
    Inventors: David S. Wright, Guy N. Middleton
  • Patent number: 6652615
    Abstract: An improved seal and method of making is disclosed for sealing a filter element to a filter mounting. The improved seal comprises a bonding pad formed from a sintered matrix of randomly oriented metallic fiber. The bonding pad is disposed between the filter element and the filter mounting A mechanical fastener coacts between the filter element and the filter mounting for compressing the bonding pad to provide a seal between the filter element and the filter mounting. The bonding pad may be heated to create a frangible seal.
    Type: Grant
    Filed: September 17, 2001
    Date of Patent: November 25, 2003
    Assignee: Pall Corporation
    Inventors: Nathaniel R. Quick, Robert Malanga, Matthew M. Smolowitz
  • Publication number: 20030201252
    Abstract: The present invention includes a method for brazing of two objects or heat treatment of one object. First, object or objects to be treated are selected and initial conditions establishing a relative geometry and material characteristics are determined. Then, a first design of an optical system for directing heat energy onto the object or objects is determined. The initial conditions and first design of the optical system are then input into a optical ray-tracing computer program. The program is then run to produce a representative output of the heat energy input distribution to the object or objects. The geometry of the object or objects, material characteristics, and optical system design are then adjusted until an desired heat input is determined.
    Type: Application
    Filed: April 29, 2003
    Publication date: October 30, 2003
    Inventors: John O. Milewski, Vivek R. Dave', Dane Christensen, Robert W. Carpenter
  • Publication number: 20030178394
    Abstract: An electrical connector is soldered or affixed to a conductive element of a glass sheet of a vehicular window via radiation heating of a layer of solder with an infrared radiative heating device. The heating device may include an infrared lamp and a reflector, which functions to direct the radiant energy from the lamp to a target region generally corresponding with the location of the solder layer between the electrical connector and the conductive element. The heating device is operable to rapidly and substantially heat the solder layer to a desired temperature to melt the solder layer, while substantially limiting directing of heat to the glass sheet. The electrical connector may be affixed at a vehicular or modular window assembly plant, such that the glass sheet may be transported from a glass manufacturing plant to the vehicular or modular window assembly plant without the electrical connector.
    Type: Application
    Filed: January 17, 2003
    Publication date: September 25, 2003
    Inventor: William A. Johnson
  • Patent number: 6426486
    Abstract: Optical heat-generating apparatus and methods that rapidly, controllably deliver energy (heat) to heat shrink tubing disposed over wires or other components and that may be used to fuse insulated wires together, and solder and unsolder packaged IC chips. In general, the apparatus comprises a housing having one or more reflective cavities that each comprise a linear elliptical reflective surface having first and second focal lines, and into which the heatable component is inserted and disposed along the first focal line. One or more optical heat-generating elements are disposed along the second focal line of each respective linear elliptical reflective surface that emit energy that is focused by the one or more linear elliptical reflective surfaces onto the heatable component disposed along the first focal line. A number of different embodiments of the apparatus have been developed. Lengths of heat shrink tubing may be readily shrunk using various embodiments of the present invention in less than one second.
    Type: Grant
    Filed: June 16, 2000
    Date of Patent: July 30, 2002
    Assignee: Judco Manufacturing, Incorporated
    Inventor: Stephen Bartok
  • Patent number: 6384366
    Abstract: A method and apparatus are provided for reliably heating the bonding areas of a substrate and/or a die or dies of a stacked die assembly or a flip-chip assembly to ensure high-quality solder or wire bonds between the substrate and the die. Embodiments include heating the wire bonding areas of the dies of a stacked die package with infrared radiation with an infrared lamp or gun directed towards the top surfaces of the dies before and during the wire bonding process, or heating the bonding pad area of the top surface of a substrate to which a flip-chip is to be mounted from above with infrared radiation from a lamp or gun to the desired temperature, then bonding the flip-chip to the substrate. The use of infrared radiant heating directed at the top surfaces of the dies and/or the substrate ensures that their respective bonding areas are heated to the proper temperature within the necessary time period, thereby enabling high-quality wire bonding or die bonding, and increasing yield.
    Type: Grant
    Filed: June 12, 2000
    Date of Patent: May 7, 2002
    Assignee: Advanced Micro Devices, Inc.
    Inventor: Pak C. Wong
  • Patent number: 6380513
    Abstract: A process for fastening a miniaturized component (2), in particular assembled in a modular manner, on a baseplate (1) by a solder joint is described. A side (4) of the component (2) is coated with a layer (5) of solder material, and the baseplate (1) is at least partly coated with a layer of metal (6, 6′, 6″). The component (2) is arranged above the baseplate (1), the metal layer and the layer (5) of solder material being a vertical distance apart and not in contact with one another. Heat energy is then supplied from the side of the baseplate (1) for melting solder material of the layer (5) of solder material on the side (4) of the component (2) until a drop forms, with the result that the drop (5′) of solder material fills the space between the component (2) and the baseplate (1) for mutual fastening.
    Type: Grant
    Filed: October 13, 2000
    Date of Patent: April 30, 2002
    Assignees: Leica Geosystems AG, MTA Automation AG
    Inventor: Christian Remy De Graffenried
  • Patent number: 6307176
    Abstract: A light beam heating apparatus having a condensing lens mechanism including an aspherical lens and a spherical lens disposed in a light path. The light beam heating apparatus also includes a light source and a light path which transmits the light beam irradiated from the light source, to an object to be heated. The light beam is transmitted through an optical fiber along part the light path, and the aspherical lens and spherical lens are disposed on the optical fiber side and on the object-to-be-heated side respectively. The above-described construction functions to suppress lateral aberration when the diameter of an optical fiber in use is changed, thereby preventing deterioration of the imaging capacity. Also, the occurrence of chromatic aberration can be suppressed to a minimum. Thus, energy concentration in the light condensing section can be improved.
    Type: Grant
    Filed: October 6, 1999
    Date of Patent: October 23, 2001
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Shinsuke Kurahashi, Nobuyuki Haji
  • Patent number: 6301436
    Abstract: A photothermic desoldering unit includes a console provided with a switch and a temperature control knob, and a working frame mounted on a top of the console. A light source is provided in the working frame and an aluminum plate is fixed near an open top of the working. frame to close the same and reflect light emitted from the light source. Temperature sensors are provided at an inner side of the aluminum plate to sense a surface temperature thereof. Power supply to the light source and luminance of the light source are controlled by the switch and the temperature control knob, respectively. When a surface temperature of the aluminum plate sensed by the sensors is the same as a temperature value set through the temperature control knob, power supply to the light source is disconnected.
    Type: Grant
    Filed: October 12, 2000
    Date of Patent: October 9, 2001
    Inventor: Yu-Ju Hsiao
  • Patent number: 6291806
    Abstract: The process of bonding a first workpiece to a second workpiece is disclosed comprising the steps of fabricating a sintered bonding pad formed from a matrix of randomly oriented metallic fibers. The bonding pad is interposed between the first and the second workpiece and the first and second workpieces are biased into engagement with the bonding pad. Heat is applied to the first workpiece to the second workpiece for transforming substantially all of the metallic fibers into a liquid for bonding the first workpiece to the second workpiece.
    Type: Grant
    Filed: September 30, 1999
    Date of Patent: September 18, 2001
    Assignee: USF Filtration and Separations Group, Inc.
    Inventors: Nathaniel R. Quick, Tao Li, Robert Malanga
  • Patent number: 6278562
    Abstract: A filter for absorbing electromagnetic radiation which is used in heating a welding zone wherein a first part is joined to a second part. The filter includes a filter housing which contains a chamber within which a fluid is placed. The fluid absorbs undesired wavelengths of radiation from a heating source before the radiation reaches the welding zone. A heat exchanger may be connected to the filter in order to cool the fluid during the filtering process.
    Type: Grant
    Filed: July 9, 1999
    Date of Patent: August 21, 2001
    Assignee: Branson Ultrasonics Corporation
    Inventor: Donald C. Lovett
  • Patent number: 6204471
    Abstract: To provide parts soldering apparatus and method which improve the productivity during parts soldering and increase the mounting accuracy of parts on a circuit board. The parts soldering apparatus of the present invention has: a stage for positioning a circuit board whereon, the circuit board is mounted a solder tip whereon; a loading arm made of a light-transmitting material, for loading a part onto the solder tip; a fluctuating mechanism for pressing the loading arm toward the circuit board; and an optical source for irradiating light onto the part through the loading arm and for melting the solder tip by the conductive heat of the light irradiated onto the part.
    Type: Grant
    Filed: February 12, 1999
    Date of Patent: March 20, 2001
    Assignee: NEC Corporation
    Inventor: Mitsuru Kurihara