US2485829A - Apparatus for and method of electrooptically scanning and reproducing recorded oscillations - Google Patents

Apparatus for and method of electrooptically scanning and reproducing recorded oscillations Download PDF

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US2485829A
US2485829A US666875A US66687546A US2485829A US 2485829 A US2485829 A US 2485829A US 666875 A US666875 A US 666875A US 66687546 A US66687546 A US 66687546A US 2485829 A US2485829 A US 2485829A
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oscillation
light
scanning
record
variations
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Holst Gilles
Vermeulen Roelof
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005—Reproducing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R13/00—Arrangements for displaying electric variables or waveforms
    • G01R13/38—Arrangements for displaying electric variables or waveforms using the steady or oscillatory displacement of a light beam by an electromechanical measuring system
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/24—Signal processing not specific to the method of recording or reproducing; Circuits therefor for reducing noise
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
    • G11B7/003—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with webs, filaments or wires, e.g. belts, spooled tapes or films of quasi-infinite extent
    • G11B7/0032—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with webs, filaments or wires, e.g. belts, spooled tapes or films of quasi-infinite extent for moving-picture soundtracks, i.e. cinema

Definitions

  • the invention relates to a method for electrooptically scanning and reproducing, oscillation records, inter alia sound tracks.
  • these records may be produced as amplituderecords, i. e. records of variable width and constant transparency or again as intensity records of constant width.
  • the invention does not relate, however, to combinations of the above-mentioned kinds of records.
  • oscillation records according to the invention is based on principles quite different from those of the known methods of reproduction. It is in general possible to distinguish two elements in oscillation records, which elements jointly determine those properties of these records which are essential for the reproduction. These elements are the degree of transparency of the track and the width of the transparent track.
  • the instantaneous width of the track is determined by the instantaneous value of the sound pressure to be recorded, this width being consequently decisive for the sound to be reproduced.
  • the degree of transparency is only influenced by deterioration of the track and by dirt present on it.
  • the amplitude to be reproduced determines the distance between this line and one of the sides of the track.
  • the invention has for its object to scan the oscillation records electro-optically and to reproduce them electrically in such manner that the dirt always present on the record and the deterioration of the track cannot contribute tothe reproduction.
  • the oscillation record is scanned by a pencil of light which moves at a high frequency perpendicularly to the axis of the track.
  • the light transmitted by the track or reflected in the case of tracks which are to be scanned episcopically, is supplied to a photoelectric element wherein the variations of the incident light are converted into variations of electric voltage.
  • the latter variations are supplied to a device wherein only that out of the two properties of the record (degree of transparency and width of the transparent track) is selected and amplified which determines the oscillation to be reproduced whereas theelement which" comprises the irregularities in the sound track which give'rise to the production of the background noise 'is' eliminated or at least/substantially eliminated;
  • Tl'ie'scanning 'of'thetrack has to-be'efiected at' so high a frequency that during a single'scanning"
  • the record is not displaced to an appreciable extent since otherwise there would be produced the same distortion which occurs in the case of an oblique scanning slit. If required, this distortion may be completely avoided by arranging that the scanning ray of light moves in a direction oblique to the axis of the track.
  • the scanning frequency must exceed the highest frequency of the oscillation record and it must be easy to separate it therefrom by electric means.
  • a scanning frequency of at least 50,000 cycles per second. The maximum scanning frequency is determined by the properties of the scanning, reproducing and amplifying devices.
  • a record produced by amplitude recording is scanned by means of the method according to the invention only the element width of the track, that is to say in every scanning period the duration of the transmitted light, is decisive for the instantaneous amplitude.
  • the element degree of transparency includes all the deviations due to dirt present in the track and due to deterioration of the latter. According to the invention, the latter element is kept remote from the reproduction by means of a suitable electric blocking device.
  • variable density recording is characterized by a constant transparency, provided there are no irregularities present, and a constant time duration, fixed by the width of the path, for each scanning cycle.
  • Deterioration of the track or the presence of dirt thereon is manifested by a local decrease of the transparency, that is to say by a decrease of short duration of the intensity of the scanning light, for dirt is nearly always opaque to light. It has been found in practice that scratches and the like cause such a refraction of light that the Scanning light does not strike the photocell or strikes the latter to a lesser degree.
  • the maximum luminous intensity of this period is measured and utilized for the reproduction.
  • the distance, i. e. the period of time, between the production of the light variation due to the oscillogram line and the end of the scanning period is measured by electric means.
  • dirt and the like may only give rise to troublesome parasitic noises if the dirt is located exactly on the narrow transparent line.
  • the possibility thereof is considerably smaller than with an ordinary track, even when in the case of slight modulation the width of the track decreases.
  • Fig. 1 represents a device for scanning sound tracks with the use of the method according to the invention.
  • Fig. 2 graphically shows the variation of the intensity of the light falling on the photo electric element during the scanning of a sound track of varying width.
  • Figures 2a and 2b represent cross-sectional views of light beams employed according to the invention.
  • Figs. 3 and 4 represent a circuit-arrangement for amplifying the sound frequencies to be scanned and for making them audible.
  • Fig. 5 shows the variation of the electric voltages originating from the photo-electric element, in the different stages of the amplifying device.
  • Fig. 6 represents a further embodiment of a circuit-arrangement for making audible the oscillations to be scanned.
  • Fig. '7 graphically shows the course of the current curves in the circuit arrangement according to Fig. 6.
  • Fig. 8 graphically represents the variation of the luminous intensities on the photo-electric element during the scanning of a sound track produced by intensity recording.
  • Fig. 9 represents a circuit arrangement for amplifying the luminous intensities according to Fig. 8 and for making these intensities audible and Fig, 10 graphically represents the variation of the alternating voltages in the different stages of this circuit arrangement.
  • Fig. 11 graphically represents the variation of the luminous intensities 'on the photo-electric element during the scanning of a sound track consisting of a transparent line of constant width but of varying position.
  • Fig. 12 represents a circuit arrangement for amplifying the oscillations according to Fig. 11 and for making them audible.
  • Fig. 13 graphically represents the current curves in the various parts of the circuit arrangement according to Fig, 12.
  • ll denotes a cathode ray tube provided in the usual manner with the required electrodes and with a source of voltage for generating an electron beam in this tube.
  • This electron beam impinges upon a luminescent screen II and forms a light spot thereon.
  • the direction of this electron beam may be modified in a plane perpendicular to the axes of coils l2 by supplying electric currents to these coils so that. the position of the light spot on the screen H is also variable.
  • a generator l3 which generates a high-frequency oscillation this electron beam is moved to and fro at a high frequency so that the light spot on the screen H also moves to and fro according to straight lines.
  • On the said screen a luminous line It is visible to the eye.
  • the character of the movement of the light spot is determined by the shape of the current curve of the generator l3. If the latter generates a sawtooth oscillation, the light spot moves uniformly from the one end to the other during a determined period of time. Then the return takes place in an extremely short time. It is also possible to cause the generator to produce a triangle oscillation. In this case the light spot is moved regularly to and fro.
  • Fig. 2 graphically represents the variation of the luminous intensity during the scanning of the sound track ll of film band l6 produced by amplitude recording. The time has been plotted as the abscissa whereas the ordinate represents the intensity of the light falling upon the photocell.
  • the cathode ray tube I0 is controlled by a sawtooth oscillation produced by the generator l3 so that the period of time during which the light spot returns from the one extreme position into the initial position is very short in comparison with the scanning time 20.
  • the image of the light spot passes over the blackened portion ill of the sound track ll so that substantially no light reaches the photocell in.
  • the transparent portion 22 of the sound track is crossed in, during which movement all the light of the light spot falls upon the photocell.
  • any interruption of short duration such as is caused by the dirt in the sound track, for example 24, which gives rise to the production of the known background noise, is not applied to the reproducing apparatus, this noise being thus eliminated in the reproduction.
  • FIG. 3 A circuit arrangement by means of which such interruptions of short duration can be eliminated is described in detail with reference to Fig. 3.
  • a beam of light 25 as shown in Fig. 2a which has a silght length in the direction of the movement of the light spot over the sound track or of a light beam as shown in Fig. 2b which consists in this direction of two parts 26, 20.
  • the light intensity falling upon the photocell l9 never falls to the zero value so long as in the direction perpendicular to the axis of the sound track the light interruption is smaller than the length of the light spot 25 of Fig. 2a or than the joint lengths of the two light spots 26 of Fig. 2b.
  • the voltages originating from the photocell l9 are supplied, with the interposition of the usual coupling elements, to the control grid of a pentode electron tube .29 which operates with an anode voltage which is lower than the normal anode voltage.
  • the anode-grid characteristic curve of such a tube is represented attli in Fig. 5. This characteristic curve is fairly steep and in the neighbourhood of the zero value of the grid voltage it exhibits a fiat portion 3! wherein the anode current no longer varies even if the grid voltage were to vary slightly. This fact is utilized to ensure that the minimal alternating voltages 32 of the photocell l9, which are due to the minimal illumination through the blackened portion of the sound track and to the noise produced by the photocell, fall within this region.
  • the variation of the area between every two successive waves 37 is, however, proportional to the variation in the scanning times tzz of the transparent portion of the sound track IT.
  • the frequency of this variation is exactly the frequency of the scanned sound record ll, which is located in the range of theaudible frequencies and which is consequently transmitted by the filter 35.
  • the above-described circuit arrangement integrates, so to speak, the alternating voltages over the limited time. At the input of the amplifier 36 there consequently arrive only alternating voltages which are proportional to the oscillations recorded in the sound track ll. They are amplified in an amplifier 36 and supplied to a reproducing loudspeaker 3B. The electric alternating voltages set up due to dirt on the track and to the noise in the photocell are consequently not reproduced.
  • Fig. 4 represents a circuit-arrangement with the aid of which likewise the light variations according to Fig. 2 can be made audible without the background noise of the sound track being also reproduced.
  • a beam of light 40 which is, in contradistinction to those beams shown in Figs. 2a and 2b, as small as is still compatible with the requirements of suflicient luminous intensity for the photocell.
  • a beam of light which has a diameter of microns so that with a velocity of the film of 45.6 cms. per second oscillations of a frequency of 11,000 cycles per sec. can still be scanned.
  • Fig. 6 represents a circuit arrangement with the aid of which the result obtained is similar to that of the circuit arrangement according to Fig.
  • the photocell l9 supplies to the grid of the tube 43 a voltage whose variation is graphically shown by curve 45 in Fig. 7. Owing to the application of this voltage the value of the grid voltage of the tube 43 varies so that the anode-grid characteristic curve 46 is displaced towards a smaller negative voltage.
  • the operating point 43 of the tubes is fixed in the single common point between the characteristic curves 56 and M. So long as the voltage applied decreases insufiiciently to cause such a rise of the negative grid voltage that the characteristic curve 46 leaps over to the other common point 69, the tubes continue to operate in the point 38. The operating point can consequently be displaced from 38 to 49 only by voltage variations in curve $5 which exceed a determined value.
  • Fig. 8 represents the variation of the light intensity on the photocell if a sound track produced by intensity recording is scanned.
  • the scanning time is plotted on the abscissa whereas the ordinate represents the intensity of the light falling upon the photocell.
  • the cathode ray tube I0 is assumed to be controlled by a sawtooth oscillation originating from the generator so that the period of time during which the light spot returns from the one extreme position to the initial position is very short in comparison with the scanning time 7352.
  • the image of the light spot passes over the black edges 50 of the sound track 5!, which edges are always present in sound tracks produced by intensity recording for the purpose of limiting the track.
  • the film particles which generally deposit on a sound track are nearly always opaque.
  • Transparent particles and also superficial scratches in the film emulsion cause a refraction such that part of the incident light does not fall upon the photocell. These particles and scratches therefore may be considered as opaque with respect to the photocell.
  • the photocell currents are supplied to a circult arrangement which only responds to the maximum intensities 54.
  • a circuit arrangement for peak rectification is shown in Fig. 9.
  • the light of the light beam 60 which passes through the sound track 5! and falls upon the photocell it sets up in the latter alternating en a es voltages which are graphically represented by voltage fill which is set up by the maximum Owing to the presence of the rectifier 58, which only allows the pasluminous intensity 54.
  • the capacitor discharge in the cessive oscillations of the highest sound frequency that is to be transmitted.
  • this capacitor has connected in parallel with it a resistor 63 which has a high value as compared with the reactance of the capacitor 59" at the scanning frequency, which amounts, for example, to 60,000 cycles per second.
  • this resistor 63 must, however, be of the same order of magnitude. as the reactance of the capacitor '9.
  • Fig. 11 represents an oscillogram consisting of a bright line I! of constant width in an opaque surrounding Hi. This line is scanned bya light spot which moves to and fro at a high frcquency in a direction perpendicular to the axis of the track Hi.
  • Curve 5?. represents graphicallythe variation of the luminous intensity falling upon the photocell.
  • the luminous intensity increases dur-- ing a short time l3 to a determined value.
  • the variation of the time interval lib-M during a plurality of scanning periods is consequently the for the course of the line ii, that is to say for the amplitude and the frequency or the oscillogram.
  • Fig. lZ' represents a circuit arrangement with the aid of which the above-mentioned period of time Hi -M is measured and is made suitable for reproduction.
  • a beam of light Ail of minimumv dimensions that is to say a beam having a diameter of about impinges upon the photocell i9 after having moved to and fro over the track '10.
  • the cathode of the photocell i9 is directly coupled with the control grid of gasfilled triode 16.
  • the anode of this triode is fed by the voltage of the generator H which also controls the backward and forward movement.
  • 59 must be able, however, totime interval between two sue-- of the-light spot.
  • a rectifier 1! so that the voltage is allowed to pass only in one determined direction.
  • the anode 5 circuit of the gasfilled triode it has coupled in parallel with it a capacitor 18 which is charged at the beginning of every scanning period by the generator l3 via a rectifier ll. It is only possible for the capacitor to discharge through in the gasfilled triode l6. So long as there is no voltage at the grid. of this triode this circuit is, however, open so that the capacitor cannot be discharged.
  • a method of reproducing an oscillation recorded on a carrier having irregularities normally producing background noise in the repro- These modes of realisation do duction of said oscillation comprising the steps of scanning said carrier transversely of the axis thereof with a pencil of light rays and at a frequency greater than frequency of said oscilla tion, collecting the light rays impinging on the carrier, converting said collected light rays to produce electric current pulses having amplitude and duration variations proportional to the amplitude and duration of the collected light, selectively translating said current pulses having amplitude and duration variations corresponding to said oscillation and suppressing said current pulses having variations corresponding to said irregularities, and translating said translated current pulses to reproduce said oscillation free from background noise.
  • Apparatus for reproducing an oscillation recorded on a carrier having irregularities normally producing background noise in the reproduction of said oscillation comprising means to scan said carrier transversely of the axis there of with a pencil of light rays and at a frequency greater than frequency of said oscillation, a photo-electric element arranged to produce electric current pulses having amplitude and duration variations proportional to the amplitude and duration variations of the light rays impinging on said carrier, means to selectively translate said current pulses having amplitude and duration variations corresponding to said oscillation and to suppress said current pulses having variations corresponding to said irregularites, and means to convert said translated current pulses to reproduce said oscillation substantially free from background noise.
  • a method of reproducing an oscillation recorded on an optically reproducible oscillation record having width Variations proportional to the amplitude variations of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said record across the width thereof with a pencil of light rays and at a frequency greater than frelating said amplified current pulses to reproduce said oscillation free from background noise.
  • a method of reproducing an oscillation recordable on an optically reproducible recording medium having width variations proportional to the amplitude of said oscillation, said medium having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said medium across the width thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, collecting the light rays impinging on the medium, converting said collected light rays to produce electric current pulses having amplitude and duration variations proportional to the width variations of said oscillation and of said irregularities, selectively amplifying said current pulses having duration variations exceeding a predetermined value corresponding to said oscillation and suppressing said current pulses having variations corresponding to said irregularities, and translating said amplified pulses to reproduce said. oscillation free from background noise.
  • a method of reproducing an oscillation the amplitude variations of which are recorded on an optically reproducible record as a function of the width of a transparent area of said record, said transparent area having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said record across the width thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, collecting the light rays impinging on the record, converting said collected light rays to produce electric current pulses having amplitude and duration variations proportional to the width of said transparent area and of said irregularities, selectively amplifying said current pulses having duration variations exceeding a predetermined value corresponding to said oscillation, filtering out current pulse having variations corresponding to said irregularities, and translating said amplified pulses to reproduce said oscillation free from background noise.
  • a method of reproducing an oscillation recorded on an optically reproducible record having width variations proportional to amplitude variations of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said record across the width thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, the cross-section of said pencil of light rays determined by the plane of said record being shaped to extend beyond edges of said irregularities in the direction of said scanning, collecting the light rays impinging on the record, converting said collected light rays to produce electric current pulses having amplitude and duration variations proportional to the width variations of said record and of said irregularities, selectively amplifying said current pulses having encased duration. variations; exceeding: a predetermined: valuecorresponding: to? said oscillation, filtering:
  • Apparatus for reproducingv an oscillationthe-amplitude of whichis recorded-onan optical-- 1y reproducible'record: as a function'of the transparency thereof, said: record havingirregularities normally producing background noise in thereproduction of said .oscillation-,. comprising means to scan saidrecord transverselyoftheaXis-thereof witha pencil oflight rays and'at a frequency greater than the frequency of said oscillation, means responsive to-the light rays; impinging on said carrier to produce: electric current pulses having amplitude and: duration variations pro-- portional tothe transparency; of said carrier and said irregularities, means selectively.
  • A. method of reproducing an oscillation recorded on an: optically reproducible record having density variations proportional to the amplitude of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said record transversely of the axis thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, collecting the light rays impinging on the record, converting said collected light rays toproduce electric current pulses having amplitude variations proportional to the density of said record, selectively rectifying said pulses to produce a potential varying correspondingly to the maximum and minimum density of said record to suppress variations of said current corresponding to said irregularities, smoothing said rectified potential, and converting said smoothed potential variations to reproduce said oscillation free from background noise.
  • Apparatus for reproducing an oscillation recorded on an optically reproducible record having density variations proportional to the amplitude of said oscillation comprising means to scan said record transversely of the recording axis thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, a photoelectric cell circuit responsive to the light rays impinging on said record. to produce pulses having amplitude variations proportional to the density of said carrier, 21. rectifier circuit coupled to said photoelectric cell circuit to produce a direct potential corresponding to the maximum value of said pulses, and electric filter coupled to said rectifier circuit to smooth said direct potential, and means to employ said fill tered potential to reproduce said oscillation.
  • a method of reproducing an oscillation recorded on an optically reproducible record having a line spaced from the edge of said record in proportion to the amplitude of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising the steps of scanning said record transversely of the axis thereof with a pencil of light rays and at a frequency greater than frequency of said oscillation, collecting the light rays impinging on the carrier, converting said collected light rays to produce electric current pulses having duration variations proportional to the distance variations of said line and .said irregularities with respect to the edge of said record, selectively amplifying said current pulses having duration variations corresponding to the distance variations of said line with respect to the edge of said carrier and suppressing said current pulses having variations corresponding to the distance variations of said irregularities with respect to the edge of said record, and converting said amplified pulses to reproduce said oscillation free from background noise.
  • Apparatus for reproducing an oscillation recorded as an oscillogram on an optically reproducible record having opaque and transparent areas, the amplitude of said oscillation being proportional to the distance of said oscill'ogram from the-edge of said record comprising means to scansaid record. transversely of of with a pencil oiligh'tirays' and. at greater than frequency of said oscillation, means record to produce; pulses having. amplitude. and"- duration variations proportional to the transparency of said record, an amplifier circuit, means to apply said pulses to said amplifier circuit to produce in the output thereof a potential proportional to the distance variations of said oscillogram with respect to the edge of said record,
  • Apparatus for reproducing an oscillation recorded on an optically reproducible record having transparency variations proportional to the amplitude variations of said oscillation comprising a cathode-ray tube having means to generate an electron beam, 9, pair of deflection electrodes and a fluorescent screen upon which said beam impinges to form a light spot, a high frequency oscillation generator coupled to the deflection electrodes of said tube to oscillate said light spot across said screen at a rate higher than the frequency of said oscillation, means to project an optical image of said oscillating light spot upon said record normal to the reproducing axis thereof, a photoelectric cell arranged to intercept light rays from said oscillating light spot passing through said record to produce electric current pulses having amplitude and duration variations proportional to the transparency of said record, means to transmit said current pulses having amplitude and duration. variations exceeding a predetermined value, and means to convert said transmitted current pulses to reproduce said oscillation.
  • Apparatus for reproducing an oscillation recorded on an optically reproducible record having width variations proportional to amplitude variations of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising a cathode-ray tube having means to generate an electron beam, a pair of deflection electrodes and a fluorescent screen upon which said beam impinges to form a light spot elongated in shape, a high frequency oscillation generator coupled to the deflection electrodes of said tube to oscillate said light spot across said screen in the direction of said elongation and at a rate higher than the frequency of said oscillation, means to project an optical image of said oscillating light spot upon said carrier normal to the axis thereof, a photo-electric cell arranged to intercept light rays from said oscillating light spot passing through the transparent area of said carrier to produce electric current pulses having amplitude and duration variations proportional to the width variations of said record and of said irregularities, means selectively to transmit said current pulses having duration variations exceeding a predetermined value
  • Apparatus for reproducing an oscillation recorded on a carrier having a transparent area the width of which is proportional to the amplitude of said oscillation, said transparent area having irregularities normally producing background noise in the reproduction of said oscillation comprising a cathode-ray tube having means to generate an electron beam, a pair of deflection electrodes and a fluorescent screen upon which said beam impinges to form a pair of light spots, a high frequency oscillation generator coupled to the deflection electrodes of said tube to oscillate said light spots across said screen in the direction connecting said spots and at a rate higher than the frequency of said oscillation, means to project an optical image of said oscillating light spots upon said carrier normal to-the axis thereof, a photo-electric cell arranged to intercept light rays from said oscillating light spots passing through the transparent area of said carrier to produce electric current pulses having amplitude and duration variations proportional to the width of said transparent area and said irregularities, means selectively to transmit said current pulses having amplitude and duration variations exceeding a predetermined
  • Apparatus for reproducing an oscillation recorded on an optically reproducible record having width variations proportional to the amplitude variations of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising a cathode-ray tube having means to generate an electron beam, a pair of deflection electrodes and a fluorescent screen upon which said beam impinges to form a light spot, a high frequency oscillation generator coupled to the deflection electrodes of said tube to oscillate said light spot across said screen at a rate higher than the frequency of said oscillation, means to project an optical image of said oscillating light spot upon said record normal to the axis thereof, a photo-electric cell arranged to intercept light rays from said oscillating light spot impinging on said record to produce pulses having amplitude and duration variations proportional to the width variations of said record and of said irregularities, a filter circuit coupled.
  • Apparatus for reproducing an oscillation recorded on an optically reproducible record having transparency variations proportional to the amplitude of said oscillation, said record having irregularities normally producing background noise in the reproduction of said oscillation comprising a cathode-ray tube having means to generate an electron beam, a pair of deflection electrodes and a fluorescent screen upon which said beam impinges to form a light spot, a high frequency oscillation generator coupled to the deflection electrodes of said tube to deflect said light spot across said screen at a rate higher than the frequency of said oscillation, means coupled to said generator to blank out said spot on the return deflection thereof, means to project an optical image of said oscillating light spot upon said record normal to the reproduction axis thereof, a photoelectric cell arranged to intercept light rays from said oscillating light spot impinging on said record to produce pulses having amplitude and duration variations proportional to the width variations of said record and said irregularities, a peak rectifier element coupled to said photoelectric cell to produce a direct potential proportional to the
  • a method of reproducing sound from a sound track on a record which comprises scanning the sound track in elementary paths transversely of its length, establishing a current pulse for each scanning path, the amplitude of each pulse being dependent u on the transparency of an elementary area of the scanning path at any instant, translating said pulses into pulses of limited uniform amplitude, integrating said translated pulses into a variable current, and translating said variable current into sound.
  • a method of reproducing sound from a sound track on a record which comprises establishing a series of current impulses varying in amplitude in accordance with the transparency of successive elementary areas in transverse paths across said sound track, one pulse being established for each transverse path in said sound track, limiting the amplitude of said pulses to a predetermined value, integrating said limited pulses to produce a variable current, and translating said variable current into sound.
  • a method of reproducing sound from a sound track on a record which comprises scanning the sound track according to elementary paths transversely of its length, establishing a current pulse for each scanning path, the value of each pulse varying in accordance with variations in transparency of successive elementary areas of the respective scanning path, and the length of each pulse corresponding to the width of the clear portion of the sound track at the point of scanning, transmitting said pulses through a current limiter to limit the amplitude thereof, translating said amplitude limited pulses into a variable current, and translating said variable current into sound.
  • a method of reproducing sound from a sound track on a record which comprises scanning the sound track according to elementary paths transversely of its length, establishing a current pulse for each scanning path, the value of each pulse varying in accordance with variations in transparency of successive elementary areas of the respective scanning path, and the length of each pulse corresponding to the width of the clear portion of the sound track at the point of scanning, transmitting said pulses through a current limiter to limit the amplitude thereof, translating said limited pulses into pulses having amplitudes proportional to the lengths of the corresponding scanning pulses, translating said variable amplitude pulses into a variable current, and translating said variable current into sound.
  • Apparatus for reproducing sound from a sound track on a record comprising, in combination, means for scanning a sound track in elementary paths transversely of its length and establishing a current pulse for each scanning path which varies in amplitude in accordance with the transparency of the successive elementary areas in the corresponding path, a current limiter, means for transmitting said variable pulses through said limiter whereby the amplitudes thereof are limited to a predetermined value, means for integrating said limited pulses into a variable current, and means for translating said variable current into sound variations.

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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US2681382A (en) * 1950-08-11 1954-06-15 Earl D Hilburn Video recording and reproducing
US3187114A (en) * 1958-08-14 1965-06-01 Raymond R Mcdaniel Recording and reproduction of intelligence signals
US3975598A (en) * 1973-05-17 1976-08-17 Westinghouse Electric Corporation Random-access spoken word electron beam digitally addressable memory
US4184055A (en) * 1977-03-18 1980-01-15 Dolby Laboratories, Inc. Scanning system for reproduction of optical sound tracks with clear area noise discriminator delay means
US4223188A (en) * 1977-03-18 1980-09-16 Dolby Laboratories, Inc. Scanning system for reproduction of optical sound tracks with clear area noise discriminator delay means
US4338684A (en) * 1974-08-27 1982-07-06 Dolby Laboratories, Inc. Scanning system for reproducing side-by-side optical sound tracks
US4596008A (en) * 1983-08-25 1986-06-17 Beard Terry D Optical sound track playback apparatus and method
US5237559A (en) * 1991-09-05 1993-08-17 Dolby Laboratories Licensing Corporation Reproduction of sound track signals by varying the detector threshold level as a function of the transverse scan position
US5543868A (en) * 1993-05-25 1996-08-06 Sony Cinema Products Corporation Method and apparatus of reproducing a digital signal recorded on a movie film

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2605162A (en) * 1949-07-27 1952-07-29 John F Gantt Film opaquing device and process
US2681382A (en) * 1950-08-11 1954-06-15 Earl D Hilburn Video recording and reproducing
US3187114A (en) * 1958-08-14 1965-06-01 Raymond R Mcdaniel Recording and reproduction of intelligence signals
US3975598A (en) * 1973-05-17 1976-08-17 Westinghouse Electric Corporation Random-access spoken word electron beam digitally addressable memory
US4338684A (en) * 1974-08-27 1982-07-06 Dolby Laboratories, Inc. Scanning system for reproducing side-by-side optical sound tracks
US4184055A (en) * 1977-03-18 1980-01-15 Dolby Laboratories, Inc. Scanning system for reproduction of optical sound tracks with clear area noise discriminator delay means
US4223188A (en) * 1977-03-18 1980-09-16 Dolby Laboratories, Inc. Scanning system for reproduction of optical sound tracks with clear area noise discriminator delay means
US4596008A (en) * 1983-08-25 1986-06-17 Beard Terry D Optical sound track playback apparatus and method
US5237559A (en) * 1991-09-05 1993-08-17 Dolby Laboratories Licensing Corporation Reproduction of sound track signals by varying the detector threshold level as a function of the transverse scan position
US5543868A (en) * 1993-05-25 1996-08-06 Sony Cinema Products Corporation Method and apparatus of reproducing a digital signal recorded on a movie film

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