US3286032A - Digital microphone - Google Patents

Digital microphone Download PDF

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Publication number
US3286032A
US3286032A US284954A US28495463A US3286032A US 3286032 A US3286032 A US 3286032A US 284954 A US284954 A US 284954A US 28495463 A US28495463 A US 28495463A US 3286032 A US3286032 A US 3286032A
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US
United States
Prior art keywords
microphone
matrix
code
digital code
motion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US284954A
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English (en)
Inventor
Baum Elmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TDK Micronas GmbH
International Telephone and Telegraph Corp
Original Assignee
Deutsche ITT Industries GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Deutsche ITT Industries GmbH filed Critical Deutsche ITT Industries GmbH
Priority to US284954A priority Critical patent/US3286032A/en
Priority to SE6461/64A priority patent/SE321709B/xx
Priority to GB22300/64A priority patent/GB1057767A/en
Priority to DE19641437468 priority patent/DE1437468A1/de
Priority to CH723864A priority patent/CH431622A/de
Priority to FR976910A priority patent/FR1397060A/fr
Application granted granted Critical
Publication of US3286032A publication Critical patent/US3286032A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation
    • H04B14/04—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using pulse code modulation
    • H04B14/044—Sample and hold circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/005—Details of transducers, loudspeakers or microphones using digitally weighted transducing elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/22—Analogue/digital converters pattern-reading type

Definitions

  • This invention relates to microphones and more particularly to a microphone capable of providing directly a digital code output.
  • Another object of this invention is to provide a minimum of equipment at the subscribers instrument to provide digital coded outputs directly from the sound waves.
  • Still another object of this invention is to provide a microphone to directly generate a digital code output representative of the sound wave impinging upon the microphone eliminating the double transformation from sound wave to electrical analog and from electrical analog to digital code.
  • a feature of this invention is to provide a microphone to convert sound waves into a given digital code comprising first means having motion imparted thereto by the sound waves, such as a diaphragm, the motion of the first means being proportional to the amplitude of the sound waves, and second means responsive to the motion of the first means to produce a digital code output according to the given digital code representative of the amplitude of the sound wave, said first and second means being an integral part of the microphone.
  • a microphone to convert sound waves into a given digital code comprising a first means having motion imparted thereto by the sound waves, the motion of the first means being proportional to the amplitude of the sound waves, second means arranged according to said given digital code, and third means responsive to the motion of the first means to activate the second means to produce a digital code output representative of the amplitude of the sound waves, said first, second and third means being an integral part of the microphone.
  • a plurality of brushes supported from a lever attached to the diaphragm to cause atent rifdce 3,235,332 ?atented Nov. 15, 1966 the brushes to scan conductive elements arranged in a code matrix to generate the digital code output.
  • a capacitor plate coupled to the diaphragm with the capacitor plate being moved to scan a second capacitor plate in the form of a code matrix to generate the digital code output.
  • Magnetic field sensitive devices arranged to be responsive to the intensity of the magnetic field varying in response to the motion of the diaphragm to generate the digital code output.
  • a further feature of this invention is the provision of a code matrix in a form other than a straight binary code, for instance delta modulation, inverted binary, excess-3 binary code, and so forth, to provide a digital output in accordance with the given selected code.
  • FIG. 1 illustrates one embodiment of the digital microphone in accordance with the principles of this invention
  • FIG. 2 is an illustration of one form which the code matrix of the various embodiments of this invention may assume
  • FIGS. 3 through 7 are schematic illustrations of other embodiments of the digital microphore in accordance with the principles of this invention.
  • FIG. 8 is an illustration of still another code matrix capable of being employed with the various digital microphone embodiments of FIGS. 1 and 3 to 9.
  • all the embodiments of the digital microphone of this invention include a first means in the form of a diaphragm having motion imparted thereto by the sound waves, the imparted motion being proportional to the amplitude of the sound waves, a second means arranged in a matrix according to a given digital code, and a third means responsive to the motion of the first means to actuate the second means to produce a digital code output periodically representative of the amplitude of the sound waves.
  • diaphragm as used herein is intended to encompass any device, such as a diaphragm of a diaphragm microphone, ribbon or cone, which is caused to move by and in accordance with a sound wave. It includes pressure, velocity and velocity gradient devices.
  • diaphragm 1 intercepting sound waves and having motion imparted thereto proportional to the amplitude of the sound wave.
  • a plurality of photosensitive devices are arranged in a code matrix 2 and a source of light 3 is disposed to be projected through a collimating device 4 upon a mirror 5 suspended from or attached to diaphragm 1. Mirror 5 will be moved in accordance with the movement of diaphragm 1.
  • the light from source 3 and collimating device 4 having a line configuration is coupled to mirror 5 and reflected therefrom to scan matrix 2.
  • a timing generator 6 will produce periodic pulses to sample matrix 2 to produce at these periodic samplings the digit outputs in accordance with the given digital code employed.
  • matrix 2 include a plurality of photosensitive devices arranged to be primed by the sampling pulse of timing generator 6 and to pass or gate an output to the digit outputs when excited by the line beam from source 3.
  • FIG. 2 illustrates a binary code matrix which could be employed as matrix 2 of FIG. 1.
  • the darkened areas constitute the photosensitive devices, such as photoelectric cells, and as illustrated, the light beam in the form of a line beam will be caused to scan this matrix to generate the binary outputs for each digit of the digital code. It is to be understood, however, that this is not the only matrix that can be employed. It would be possible to employ the reflected binary code and any of the other known types of digital codes presently available in the art.
  • the illustration of FIG. 2 is only for the purpose of an illustrative example and is not meant to limit the scope of this invention.
  • FIG. 3 another embodiment of the digital microphone of this invention is illustrated which incorporates a code matrix 7 arranged to be responsive to an electron beam in the form of a line as produced by electron gun 8.
  • Matrix 7 may be in the form of apertures through which the electron beam may pass to impinge upon target electrodes which when sampled to overcome a bias thereon will permit the production of the digit outputs.
  • Matrix 7 may also take the form of elements arranged in the code matrix in accordance with the given digital code to be responsive directly to the electron beam, but biased in such a manner that an output will not be produced until the sampling signal is applied thereto.
  • the line electron beam is caused to sweep matrix 7 by utilizing magnet 9 supported from diaphragm 1 whose motion will cause the magnetic field of magnet 9 to sweep the electron beam across the surface of matrix 7 and, hence, produce the digital code output during the sampling periods as described hcreinabove.
  • FIG. 4 there is illustrated therein still an other embodiment of the digital microphone of this invcntion which incorporates therein diaphragm 1 to interccpt the sound wave and having motion imparted thereto by the sound wave.
  • This motion is imparted to lever 10 secured to diaphragm 1.
  • Lever 10 carries thereon a plurality of brushes or contacts 11 equal in number to the digits of the digital code which are caused to sweep code matrix 12 in the form of conductors arranged in accordance with the particular digital code.
  • Matrix 12 is sampled by the sampling signal from generator 6 and the position of contacts 11 on matrix 12 will determine the digit output for the given digital code.
  • the sampling signal will be coupled to each conductor forming the code matrix secured to the front face of a dielectric sheet 14 and the'brusbes will act to connect these condoctors to a solid line conductor 13 secured to the opposite face of the dielectric sheet 14 for each of the code digits.
  • This will act to complete the circuit between the conductors arranged in the code configuration and the solid line conductors 13.
  • Another modification would be in the form of a dielectric sheet having apertures therein arranged in the code matrix and conductors 13 behind the apertures of each digit of the given digital code.
  • the sampling signal would then be applied to contacts 11. When contacts 11 sense an aperture the circuit is completed to conductors 13.
  • diaphragm 1 acts to intercept the sound wave and having motion imparted thereto proportional to the amplitud'e of the sound wave.
  • This motion is then imparted to movable capacitor plate 15 which is caused to scan a code matrix formed from a plurality of individual conductors arranged in accordance with the particular digital code.
  • the fixed capacitor plate forming the code matrix 16 and the movable capacitor plate 15 are capacitively coupled together and when plate 15 is sampled by the sampling signal from generator 6, appropriate outputs are produced at the digit outputs in accordance with the amplitude of the motion and, hence, the amplitude of the sound wave at the time of sampling.
  • FIG. 6 illustrates still another embodiment of the digital microphone of this invention including a light source 17 and a collimator 18 to produce a beam which is acted upon by polarizer 19 in the form of a Polaroid or similar polarizer with the polarized light energy being passed through pressure sensitive polarizing device 20.
  • Device 20 is coupled to diaphragm 1 to respond to the motion of diaphragm 1 through motion to pressure transducer 21.
  • the action of devices 19 and 20 may be described as follows to cause the light beam of source 17 to illuminate only that part of matrix 22 which describes the instantaneous amplitude of the input sound wave.
  • pressure sensitive polarizing device 20 by shaping and stressing it, so that at only one line, perpendicular to the applied diaphragm force, is the polarization the same as that of the polarized incident light from device 19.
  • the position of this line varies with the applied stress from diaphragm 1 such that the light passing through device 20 illuminates only the portion of the photosensitive code matrix 22 which represents the instantaneous force applied by diaphragm 1 and, hence, the amplitude of the sound wave.
  • FIG. 7 illustrates still another embodiment of the digital microphone of this inventon including magnetic field sensitive devices of solid state nature of magnetic material arranged in accordance with a given digital code to form a code matrix 23.
  • Matrix 23 may have the configuration illustrated in FIG. 2 where the darkened areas represent the magnetic material or solid state magnetic field sensitive material.
  • a magnet 24 is secured to diaphragm 1 to move in accordance with the movement of diaphragm 1. The movement of magnet 24 is imparted to arm 25 of magnetic material to scan matrix 23.
  • the magnetic field present in arm 25 saturates that particular portion of matrix 23 representing the magnitude of movement of diaphragm 1 and, hence, the amplitude of the sound wave.
  • Output pickup devices 26 such as coils or solid state device, for instance, Hall effect devices, are magnetically coupled to matrix 23 and will respond to that saturated portion of matrix 23 to produce the digital code output. If magnet 24 is an electromagnet and pulsed by the sampling signal, the output devices 26 may be coils to sense the presence of the magnetic field.
  • Another possible variation is in the code matrix itself wherein it is desired to transmit the digital code output in the form of delta modulation rather than the generally well known binary code type digital outputs.
  • One method of achieving this is to employ in conjunction with any of the motion transducers described hereinabove a matrix 27 wherein the maximum allowable amplitude is divided into a number of discrete levels 28 which may be equal or unequal.
  • the microphone is arranged to produce an output for each of the levels in such a manner as to produce a positive signal as each level is reached in increasing amplitude and a negative output as each level is reached in a decreasing amplitude.
  • These signals may be used to operate a counting device whose output is in the desired coded form. As illustrated in FIG.
  • amplitude change senser and counter 29 will cooperate with matrix 28 to produce the positive and negative signals as described hereinabove.
  • Each of levels 28 will have applied thereto a dill'ercnt value of voltage and the amplitude change senser detects whether the voltage increases or decreases as the microphone scanning arrangement moves from one level to another. The output of this senser then actuates the counter to produce the desired digital code output.
  • Fiber optics may be used to improve the performance or simplify the construction of the schemes dependent on light.
  • a microphone to convert sound waves into a given digital code comprising:
  • a microphone to convert sound waves into a given digital code comprising:
  • first means integral with said microphone having motion imparted thereto by said sound waves, said motion being proportional to the amplitude of said sound waves; second means integral arranged with said microphone arranged according to said given digital code; and third means integral with said microphone re ponsive to said motion of said first means to activate said second means to produce a digital code output representative of the amplitude of said sound waves.
  • said first means includes a diaphragm.
  • said third means includes a light polarizer to impart a given polarization to said light 'beam;
  • a pressure sensitive light polarizing device attached to said first means to control the portion of said photosensitive devices said polarized light 'beam illuminates in accordance with said motion of said first means.
  • a microphone according to claim 2 wherein said second means includes a target assembly including means arranged according to said given digital code; and said third means includes an electron gun projecting a line electron beam to said target assembly, and a magnetic means carried by said first means to sweep said beam across said assembly to activate predetermined ones of said target assembly means to produce said digital code output.
  • said second means includes a group of conductors arranged according given digital code; and said third means includes conductive means carried by said first means in juxtaposition to said group of conductors to produce said digital code output during predetermined sampling periods.
  • said conductive means includes a conductive plate capacitively coupled to said group of conductors; and said third means includes means to periodically sample said plate.
  • said second means includes magnetic field sensitive devices; and said third means includes magnetic field producing device coupled to said first means having its position varied in accordance with said motion of said first means.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Theoretical Computer Science (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US284954A 1963-06-03 1963-06-03 Digital microphone Expired - Lifetime US3286032A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US284954A US3286032A (en) 1963-06-03 1963-06-03 Digital microphone
SE6461/64A SE321709B (xx) 1963-06-03 1964-05-28
GB22300/64A GB1057767A (en) 1963-06-03 1964-05-29 Digital microphone
DE19641437468 DE1437468A1 (de) 1963-06-03 1964-06-02 Digitales Mikrophon
CH723864A CH431622A (de) 1963-06-03 1964-06-03 Einrichtung zur Umwandlung von Schallwellen in digitale Signale
FR976910A FR1397060A (fr) 1963-06-03 1964-06-03 Microphone digital

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US284954A US3286032A (en) 1963-06-03 1963-06-03 Digital microphone

Publications (1)

Publication Number Publication Date
US3286032A true US3286032A (en) 1966-11-15

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Application Number Title Priority Date Filing Date
US284954A Expired - Lifetime US3286032A (en) 1963-06-03 1963-06-03 Digital microphone

Country Status (6)

Country Link
US (1) US3286032A (xx)
CH (1) CH431622A (xx)
DE (1) DE1437468A1 (xx)
FR (1) FR1397060A (xx)
GB (1) GB1057767A (xx)
SE (1) SE321709B (xx)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3435159A (en) * 1966-01-03 1969-03-25 Bell Telephone Labor Inc Circuit and method for testing complex systems
US3521271A (en) * 1966-07-15 1970-07-21 Stromberg Carlson Corp Electro-optical analog to digital converter
US3622791A (en) * 1969-06-27 1971-11-23 Patrice H Bernard Microphone circuit for direct conversion of sound signals into pulse modulated electric signals
US3663758A (en) * 1970-03-24 1972-05-16 Teaching Complements Inc Speech pattern recognition system
US4395593A (en) * 1979-11-27 1983-07-26 Bell Telephone Laboratories, Incorporated Acoustic differential digital coder
US4422182A (en) * 1981-03-12 1983-12-20 Olympus Optical Co. Ltd. Digital microphone
US4515997A (en) * 1982-09-23 1985-05-07 Stinger Jr Walter E Direct digital loudspeaker
WO1993007686A1 (en) * 1991-10-09 1993-04-15 Buchholz Jeffrey C Optical microphone with vibrating optical element
US5619583A (en) * 1992-02-14 1997-04-08 Texas Instruments Incorporated Apparatus and methods for determining the relative displacement of an object
US5995260A (en) * 1997-05-08 1999-11-30 Ericsson Inc. Sound transducer and method having light detector for detecting displacement of transducer diaphragm
US20020093881A1 (en) * 2000-10-26 2002-07-18 Kane Gerry M. Digital vibration transducer
WO2002073809A2 (en) * 2001-03-14 2002-09-19 Reveo, Inc. Electron beam excited superconducting analog-to-digital converter
US6493451B2 (en) * 1999-10-15 2002-12-10 Phone-Or Ltd. Communication helmet
US20100321698A1 (en) * 2007-07-12 2010-12-23 Thankappan Santhanakrishnan Method and apparatus for the simultaneous generation and detection of optical diffraction interference pattern on a detector
US20130230329A1 (en) * 2011-04-05 2013-09-05 Panasonic Corporation Optical microphone
US20140119737A1 (en) * 2012-10-31 2014-05-01 Vocalzoom Systems Ltd. System and Method for Detection of Speech Related Acoustic Signals by Using a Laser Microphone
US20150365753A1 (en) * 2014-06-17 2015-12-17 Thomson Licensing Optical microphone and method using the same
US20180248621A1 (en) * 2015-09-07 2018-08-30 Philips Lighting Holding B.V. Embedding data into light

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3433959A (en) * 1966-07-25 1969-03-18 Perkin Elmer Corp Microphone
CH539845A (de) * 1972-06-30 1973-07-31 Ibm Elektroakustischer Wandler
US4284858A (en) * 1979-12-06 1981-08-18 Rockwell International Corporation Dichroic transducer
DE3020247C2 (de) * 1980-05-28 1982-09-02 Franz Vertriebsgesellschaft mbH, 7634 Kippenheim Verfahren und Anordnung zur Umwandlung von Schallwellen in digitale elektrische Signale mit Hilfe von elektroakustischen Wandlern
DE3642055A1 (de) * 1986-12-09 1988-07-07 Wolfgang Dr Littmann Einrichtung zur direkten umwandlung von schall in digitale information - digitales mikrofon
DE102009032057A1 (de) * 2009-07-07 2011-01-20 Siemens Aktiengesellschaft Druckwellen-Aufnahme und Wiedergabe

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937754A (en) * 1929-11-18 1933-12-05 Rca Corp Telephony
US2173994A (en) * 1937-03-30 1939-09-26 Rca Corp Microphone
US2259511A (en) * 1937-10-14 1941-10-21 Rca Corp Microphone
US2458652A (en) * 1946-12-13 1949-01-11 Bell Telephone Labor Inc Electron discharge apparatus
US2596199A (en) * 1951-02-19 1952-05-13 Bell Telephone Labor Inc Error correction in sequential code pulse transmission

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1937754A (en) * 1929-11-18 1933-12-05 Rca Corp Telephony
US2173994A (en) * 1937-03-30 1939-09-26 Rca Corp Microphone
US2259511A (en) * 1937-10-14 1941-10-21 Rca Corp Microphone
US2458652A (en) * 1946-12-13 1949-01-11 Bell Telephone Labor Inc Electron discharge apparatus
US2596199A (en) * 1951-02-19 1952-05-13 Bell Telephone Labor Inc Error correction in sequential code pulse transmission

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3435159A (en) * 1966-01-03 1969-03-25 Bell Telephone Labor Inc Circuit and method for testing complex systems
US3521271A (en) * 1966-07-15 1970-07-21 Stromberg Carlson Corp Electro-optical analog to digital converter
US3622791A (en) * 1969-06-27 1971-11-23 Patrice H Bernard Microphone circuit for direct conversion of sound signals into pulse modulated electric signals
US3663758A (en) * 1970-03-24 1972-05-16 Teaching Complements Inc Speech pattern recognition system
US4395593A (en) * 1979-11-27 1983-07-26 Bell Telephone Laboratories, Incorporated Acoustic differential digital coder
US4422182A (en) * 1981-03-12 1983-12-20 Olympus Optical Co. Ltd. Digital microphone
US4515997A (en) * 1982-09-23 1985-05-07 Stinger Jr Walter E Direct digital loudspeaker
WO1993007686A1 (en) * 1991-10-09 1993-04-15 Buchholz Jeffrey C Optical microphone with vibrating optical element
US5262884A (en) * 1991-10-09 1993-11-16 Micro-Optics Technologies, Inc. Optical microphone with vibrating optical element
US5619583A (en) * 1992-02-14 1997-04-08 Texas Instruments Incorporated Apparatus and methods for determining the relative displacement of an object
US5621806A (en) * 1992-02-14 1997-04-15 Texas Instruments Incorporated Apparatus and methods for determining the relative displacement of an object
US5995260A (en) * 1997-05-08 1999-11-30 Ericsson Inc. Sound transducer and method having light detector for detecting displacement of transducer diaphragm
US6493451B2 (en) * 1999-10-15 2002-12-10 Phone-Or Ltd. Communication helmet
US20020093881A1 (en) * 2000-10-26 2002-07-18 Kane Gerry M. Digital vibration transducer
WO2002073809A2 (en) * 2001-03-14 2002-09-19 Reveo, Inc. Electron beam excited superconducting analog-to-digital converter
WO2002073809A3 (en) * 2001-03-14 2004-03-04 Reveo Inc Electron beam excited superconducting analog-to-digital converter
US20100321698A1 (en) * 2007-07-12 2010-12-23 Thankappan Santhanakrishnan Method and apparatus for the simultaneous generation and detection of optical diffraction interference pattern on a detector
US8643846B2 (en) * 2007-07-12 2014-02-04 Defence Research And Development Organisation Method and apparatus for the simultaneous generation and detection of optical diffraction interference pattern on a detector
US20130230329A1 (en) * 2011-04-05 2013-09-05 Panasonic Corporation Optical microphone
US9014565B2 (en) * 2011-04-05 2015-04-21 Panasonic Intellectual Property Management Co., Ltd. Optical microphone
US20140119737A1 (en) * 2012-10-31 2014-05-01 Vocalzoom Systems Ltd. System and Method for Detection of Speech Related Acoustic Signals by Using a Laser Microphone
US9344811B2 (en) * 2012-10-31 2016-05-17 Vocalzoom Systems Ltd. System and method for detection of speech related acoustic signals by using a laser microphone
US20150365753A1 (en) * 2014-06-17 2015-12-17 Thomson Licensing Optical microphone and method using the same
US9628921B2 (en) * 2014-06-17 2017-04-18 Thomson Licensing Optical microphone and method using the same
US20180248621A1 (en) * 2015-09-07 2018-08-30 Philips Lighting Holding B.V. Embedding data into light
US10727943B2 (en) * 2015-09-07 2020-07-28 Signify Holding B.V. Embedding data into light

Also Published As

Publication number Publication date
SE321709B (xx) 1970-03-16
GB1057767A (en) 1967-02-08
DE1437468A1 (de) 1968-10-10
CH431622A (de) 1967-03-15
FR1397060A (fr) 1965-04-23

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