US2478681A - Cathode-ray type sound recording system - Google Patents

Description

9, 1949- G. L. BEERS 2,478,681

CATHODE-RAY TYPE SOUND RECORDING SYSTEM Filed July 18, 1945 mew/v PUMP , INVENTOR.

Patented Aug. 9, 194?;

CATHODE-RAY TYPE SOUND RECCRDING SYSTEM George L. Beers, Haddonfield, N. J., assignor to Radio Corporation of of Delaware America, a corporation Application July 18, 1945, Serial No. 605,800

1 Claim. 1

This invention relates to the recording of sound on a photographic medium, or the like, and has for its principal object the provision of an improved apparatus and method of operation whereby sound records of the variable area or variable density types are readily produced either on a stationary recording medium or on a medium which is moved at a substantially uniform speed.

It has been proposed to record sound by means of a cathode ray tube provided with a Lenard window through which a cathode ray. or electron beam, modulated in accordance with the audio frequency signals is applied to a moving photographic strip. Proposals of this character are found in U. S. Patents 1,864,363 and 1,870,975, for example. Such sound recording devices are not altogether satisfactory for the reason that the electron beam tends to disperse due to collision with the gas molecules of the air and the fidelity of the recorded sound is impaired.

It has also beenproposed to record transient electrical phenomena by means of a cathode ray device within which is supported a photographic recording medium which is maintained stationary while'the phenomena are being recorded. A device of this character is disclosed by U. S. Patent 2,086,546 in accordance with which a timing pulse is applied to one pair of ray deflectors while a potential representative of the phenomena to be recorded is applied to another ray of deflectors.

The sound recording apparatus of the present invention is similar in some respects to the apparatus of the aforesaid Patent 2,086,546, but differs therefrom in other important respects. For example, the present invention provides a cathode ray type of sound recorder which operates (1) to record a variable area record on a moving record medium when the signals to be recorded are applied to one pair of its deflectors, (2) to record a variable density record on a moving record medium'when the signals to be recorded are applied to its control grid, or (3) to record a record in the form of a spiral on a stationary record medium when the signals to be recorded are applied to its control grid and the separate pairs of its deflectors are subjected to potentials which are in quadrature, have the same frequency and have their amplitudes varied from a relatively high value to a relatively low value, or vice Versa, as disclosed by U. S. Patent 1,470,696, for example.

One suitable means of effecting these Various results is a type of cathode ray device commonly known as an electron microscope. As is well known, the electron microscope includes an evacuated container within which may be mounted means for supporting a specimen to be examined, means for producing an electron beam, means for focusing this beam on the specimen, and means for focusing an image of the specimen on a photographic recording medium or on a viewing screen. In this type of apparatus, focusing of the electron beam at the desired points in its path is effected by means of electron lenses which may be of the electrostatic type, the electromagnetic type, or a combination of these two types. For scanning the specimen, the electron microscope may be provided with deflectors to which suitable potentials are applied for moving the beam from one point of the specimen to another.

Like the electron microscope, the sound recorder of the present invention includes means for forming, focusing and controlling the position of an electron beam. It differs from the conventional electron microscope in that it includes (1) means for forming a light slit, (2) means for moving a photographic film or strip transversely of this slit at a substantially uniform speed, (3) means for varying the position or the intensity of the beam at the slit in accordance with impulses to be recorded, (4) means for conforming the beam to a desired shape or form such that its movement with respect to the slit exposes the record medium in accordance with the applied impulses, and (5), where a spiral record is to be produced on a stationary record medium, means for applying quadrature potentials of the same frequency and varying amplitudes to the separate pairs of deflectors of the recorder. As

hereinafter explained, the light slit member may be removed from the path of the beam during the production of a record of spiral form. The means by which the beam is conformed to a predetermined shape also may be removed if not essential to the particular type of record produced at any given time.

Important objects of the invention are the provision of an improved sound recorder wherein the use of moving optical parts is avoided; the provision of a recorder which obviates halation in the photographic record medium andrealizes the full resolution capabilities of such medium; the provision of a sound recorder which is readily adapted to produce different types of records; and the provision of a recorder which affords an improvement in the signal to noise ratio due to the better recording densities made possible, and makes possible an extension of the frequency range of the recorded impulses.

The invention will be better understood from the following description considered in connection with the accompanying drawings, and its scope is indicated by the appended claim.

Referring to the drawings:

Fig. 1 is a diagrammatic view, partly in section, of a preierrediorm of; the invention,

Fig. 2 illustrates one iorm the electron beam may assume and its relation to the light slit,

Fig. 3 illustrates certain details of the record ture icrshapingthe electronj beam, a focusing anode. [6,,a second.v accelerating anode ll, pairs ofdefiectors l8 and 19 which function to move the beam in directions at right angles to one another, an -.24 member 2 having a very narrow light.sl it. 2]. It is, .of course, apparent that. the illustratedarrangement. of. these. different parts may be modified. invarious ways. without changing the 'functionsperformed by the recorder as awhole. -.For.-,example,the electronic lens formed by. theelectrodeslli and I'Lmay be replaced by an, electromagnetic lens suchas those disclosed troniclensoiany suitable type may be interposed in: the;-path-,cf,thehcam between. the light slit an her e r incmedium In any asa theoverallfunction of' the electronic;.optic al. system formed by the various elecc trodes, theaaperturedqmember I and the light s-l-iti member 20-, is-wto produce. at theT surface of a rhetqera hl reco di is;.med-i m an e ectr beam. hi hvariesin cross sectionalarea or in tensity;,i a cc danee-.-witl1;t e:audio freque c sn l icberecorded on the medium 2. us, fa switchr ais clcsedtctheleft tccQn c e id 3: .0 al ix desource of :a potentia a a witch zis clos d to :the right to conn ct th def ectors ;t =;t0.1t;he:audio .fr quency si nal term-ina1s;25,;the position-of the electr n :beam with espectto ;th,e;sl:it;,2 lzisvariedin accordance with theiappliedjaudio frequencysignaliand a variable area record is produced.

:As indicated by: Fig. 2 the aperture in themember 15 .may .be i triangular-shape so that :a beam having .the formindicatedgb-y the broken lines isvibrated transversely oizthe light :slit' 2 I If ;;the:-.switch:23 is closedto the right to conmeet the gridIfi'toithe signal-supply terminals 26 and-the deflectorsll'fland L9 are subjected to fixed potentials by which the beam is-adjusted to the required positionoil-"the light slit, the recording medium :22 is exposed to an' electron beam which is of .constant :area :and varies in intensity in accordance with the-audio-irequencysignals supplied to the termin'alsfli. -In order-that the operator. may-properly focus and predetermine the operating limitsof the electronic beam, the slit is covered by a mask il which-is coated with fluorescent material. sitioned by .a'lever '53; The lever may be arranged to .-work'.rthrough-a vacuum seal or bellows-;5.5 infith casing .nearsthe window v5'! for viewing the fluorescent mask. "The window The mask il may be po- '4 should be covered with a light tight cap when not in use, thereby to avoid exposing the film. The mask Si is pivoted at a suitable point 59.

If a sound record in the form of a spiral is to be produced, the members l5 and may be moved out of the path of the beam which, in this case, ;is focused? toa relativelyesmallr cross-sectional. area atthesurface or. the :recording medium 22, With the switches 21 and 28 closed to the right to apply to the deflectors l8 and I9 quadrature potentials which are of the same frequency and a're -gradually changed in amplitude,

and the switch 23 closed to the right to apply audio frequencyysignais to the grid i3, there is applied to" the surface of the record 22 an electron beam-.=which is of constant cross-sectional .areartracesaa spiral path, and varies in intensity or is controlled in accordance with the applied signals.

i'. pledthrough-a coupling 32. The .-cou=pling32 may be of such type as-. smooths: irregularities in the torque applied through it, -,-and;. is 1 shown. as connected to-a take-up. reel 33, although it may be connected to,.al 1y tother:suitablepart-of the drive mechanism. H

The film moving "mechanism illustrated; is I intended to be;illustratireoiany. suitable mecha= nism of the prior art whlchmay be substituted for it if desired. Itincludes a feed reel 34,;whlch may be provided with a brake or :other retard-- ing device 35 mountedwonathe end of-its-shaft.

From the. feed reel-34; the:recor.d;strip passes over a spring pressedv roller .136, over :the: rollers 31 and-38,;over the spring .presse'drroller 39, and

thence tothe take-up reel-.33. These various rollers are shown as mounted. between 1 upright members I50: and 4! which-areso fastened. to the base-of thereceptacle IOZflSftOffifiOldffiIIlllbSEJT- ings for: the various rollers and to :be;readilyxr'e-= moved; for dis ssemblin :-thermechanismi through openings provided with cair-ti'ghtpcovers 42 ian'd t3 held in-;p1ace brnollars 4.4 and :45 :which' are threaded on: opposite .sidesbfithe dowrvpa rt of the receptacle" 1 0.

The lowerz'partpfithercasing l nzis'zdivided; into two; compartments by apartit-lon fdil. .Where the shaft of the-motor :3 l passes through '.this;pa1-ti ti-on, ,thereis: provided arr air .tig'htzseal '41. Under these 1' conditions, :the yacuumqzump i-s znot required :to remove the gas otherwise glven off by theimotcr 3| nndtlie'rcouplingqfil :A:vessel 4 9 containin hygroscopic :material inay be placed inrthe receptacle I'D? for taking upm'oisture given off ,by the ;record strlpi22. zrnsteaupr using a mechanical :coup-ling. awhich zrequires a seal, 'the connection between-.the motorrs'l :and film takeup reel 33 mayzbe az'magneticrcoupling which can act through :a :thin non-magnetic plate, thus eliminating the -sneed for a xvacuum ti-ght" bearing.

Fig. 4 illustrates a z-modified electron l optical system wherein electromagnetic "focusing is employed. In this :of the "invention, the coil as focuses fthelbam-'S0i'that=the triangular shape given the beam iby $13116 rapertur'e :ofthe I-me'niber I4 is maintained at the slit 2| of the member 20. In this figure, the cathode I 2, grid I3 and first anode M are shown in the form of a block. The electromagnetic lens 48 may be of any satisfactory type such as those disclosed by U. S. Patents 2,301,987 or 2,301,303, for example.

Another method of operating the forms of the invention described above is to permanently remove the aperture and slit members l5 and 20 and to focus the beam in a fine spot directly on the film. Under these conditions, a radio frequency deflecting voltage (say 200 kc.) is applied to one pair of the deflectors. This voltage is modulated by the audio frequency signals to be recorded for producing a variable area record. For producing a variable density record, the radio frequency potential applied to the pair of deflector plates is kept at a constant amplitude and the audio signals are applied to the grid as previously indicated in connection with the spiral type of record which is recorded on a stationary record medium.

The present invention thus makes available a sound recorder which is adapted to produce various types of sound records. These records are of high quality due to the fact that they are produced by an electron beam Without the use of moving optical parts, thus better utilizing the capabilities of the photographic record medium.

What is claimed is:

In a sound recorder adapted to produce a record which is alternatively of the linear variable width type, the linear variable density type or the spiral variable density type, the combination of an evacuated receptacle having opaque walls, means for forming an electron beam of triangular cross section, means for focusing said beam at a predetermined point, means for moving a sound record medium within said receptacle along a path which includes said point, means forming a narrow slit movable into the path of said beam for restricting the area of said medium exposed to said beam, a grid for controlling the intensity of said beam, deflectors for controlling the position of said beam along paths which are perpendicular to one another, means for applying a unidirectional voltage, means for applying alternating voltages which are in quadrature, means for applying an audio frequency voltage, means for connecting said deflectors alternatively to said unidirectional voltage applying means or to said quadrature applying means, and means for connecting said audio frequency voltage applying means alternatively to said grid or to a predetermined pair of said deflectors.

GEORGE L. BEERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,470,696 Nicolson Oct. 16, 1923 1,864,363 McCreary June 21, 1932 1,870,975 Ulrey Aug. 9, 1932 1,943,109 Coolidge Jan. 9, 1934 1,997,976 Peterson Apr. 16, 1935 1,998,465 Severy Apr. 23, 1935 2,091,826 Menger Aug. 31, 1937 FOREIGN PATENTS Number Country Date 389,101 Great Britain Mar. 6, 1933 OTHER REFERENCES The Cathode Ray Oscillograph In Radio Research, published by His Majesty's Stationery Oifice, London 1933, pages to 91, inclusive.

Images