US1926406A - System for recording impulses - Google Patents

Description

Sept. 12, 1933. F. RIEBER 1,926,406

SYSTEM FOR RECORDING IMPULSES Filed sept. 3o, 1930 WIJZM?? latented Sept. 12, 1933 UNITED STATES PATENT OFFICE SYSTEM FOB RECORDING ILIPULSES Application September 30, 1930 Serial No. 485,422

12 Claims.

This invention relates to a system for record#- ing variable electrical potentials. such as are encountered in connection with recording sound on a motion picture lm.

In recording sound on motion picture films or other sensitized surfaces, use has been made of a source of light, shining through a narrow aperture. The intensity oi' this light is modulated or varied in accordance with electrical potential variations, as determined by the sound modulations present in an electric circuit. As the motion picture film is moved past this thin beam of light, a record is produced, as a varying density of the illm.

In my present invention it is proposed to bviate the need of light to aect the sensitized lm. Instead use is made of an electrostatic iield, the intensity of which varies in accordance with the vibrations to be recorded, and which it o has been found, can affect the film by the production of ions or electrons in the gas or air in which the film is disposed.

In recording these varying electrical potentials by such an electrostatic field acting on the gas in which the nlm moves, the varying electrical potentials are applied across electrodes disposed on opposite sides of the nlm. One of the electrodes can be in the form of a narrow wedge which concentrates the electrostatic field along a narrow 30 strip. However, in order to bring the ionization or the strength of the field to a point where the lm can be affected, there is apt to be a glow or corona eiect that is disturbing, because it widens out the area affected by the narrow electrode and causes blurring and distortion of the sound produced from the record. It is also impossible under such circumstances to record the higher frequencies of sound, such as 8,000 or 10,000 cycles or higher which are essential for good quality.

It is one of the objects of my invention to prevent such diiused luminous energy and to make it possible to concentrate the ionization along a narrow strip transverse to the movement of the 111m as to record even the higher sound frequencies accurately.

I accomplish this result by arranging' the electrodes betwen which the nlm is movable so that a guarding electrostatic field is produced, of comparatively low intensity and which surrounds the recording electrostatic ileld and prevents its material divergence. The surrounding or guarding ileld has a potential gradient insuiilcient to produce ionization while the marking held is intense enough to produce high ionization andV without corona eifects. Any corona present would be detrimental, because it would difIuse or blur the record.

In order further to ensure against appreciable corona effects, I provide a loading impedance in the circuits that prevents the potential gradient from reaching the stage where appreciable corona results even for large amplitude of vibrations to be recorded.

My invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of several embodiments of my invention. For this purpose I have shown a few forms in the drawing accompanying and forming part of the present specification. I shall now proceed to describe these forms in detail, which illustrate the general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a schematic diagram of a system embodying my invention;

Fig. 2 is a picture of a portion of nlm produced 3 by the aid of my invention;

Fig. 3 is a diagram of a further form of the invention; and

Fig. 4 shows a still further modincation.

In Fig. 1 there is shown a mm 11 (greatly en- 85 larged) having a sensitized layer 12 upon which the record is to be placed. This ilm 11 isintended to be progressed at a substantially uniform rate past a recording station, where an electrostatic eld is impressed upon the gas or air adjacent the nlm. In the present instance the electrostatic ileld is represented as produced by the two electrode structures 13 and 14. It is to be understood that the thickness of the film 11 and the various clearances have been exaggerated in the drawing, as ordinarily the two electrode structures would be placed so close together that there is just barely room for the nlm 11 to passrtherebetween.

The electrostatic ileld impressed across the intervening space between the electrode structures 13 and 14 is so arranged that an intense neld occurs at a localized or limited portion thereof; such as that represented by the line 15. The surrounding electrostatic field is of lower intensity and is caused to converge so as to act as a guard against the spreading of the more intense iield 15. This invention relates to the maner in which this nonhomogeneous electrostatic field is produced, whereby the intense fleld 15 serves as the recording'field to the exclusion of the possibility of recording outsidev of the limited area occupied by this eld.

.and the lower electrode 14.

In Fig. 2 the film 11 is shown carrying the record markings 18 (diagrammatically shown) which are in the form of striations of varying density depending upon the varying intensity of the field 15, land which are very closely spaced together. This type of recording is now well understood in connection with ordinary glow tube recording. With the aid of an electrostatic field as described, the fineness of the individual stria tions making up the record 16 can be made much greater than is possible with the ordinary optical glow tube system, and especially if care be taken to prevent any diffused luminous disturbances be2-- vtween the electrode structures 13 and 14. The intense field 15 is produced between a tapered electrode member 17 having a point that extends transversely to the movement of the film 11 and corresponding to the width of the record 16. This point is opposed to the electrode structure 14. on the opposite side of the film 11. The less intense or non-ionizing field 18 is; produced between a guard electrode structure 19 and the electrode structure 14. This guard electrode structure surrounds the member 17. The configuration of electrode 14 is such that the field 18 converges around the intense field 15. For example, this can be accomplished by making electrode structure 14 in the form of a metal cylinder, the axis of which is transverse to the movement of the film 11; while the guard electrode 19` covers a greater area.

The point of member l17 extends slightly below the edge of the aperture 20 through the guard electrode 19. This aperture 20 is so formed that there is an insulating space between the members 17 and 19, there being converging surfaces defining the aperture in order to assist in preventing spreading of the eld 15. In order to ensure substantial uniformity of field 18, the edges of guard member 19 may be rounded as indicated at 21.

As thus far described, it is apparent that the guarding field 18 acts vto confine the recording field 15 to a very narrow edge, the recording being accomplished by electrons or ions impacting against the sensitized surface 12.

The varying electrical potentials to be recorded by this system can be arranged to modulate either the field 18 or the field 15 to secure the varying density of the striations in record 16. In the form shown, the modulated electric potentials are impressed across electrode member 17 One way in which these are modulated is illustrated in Fig. 1.

Thus oscillator 22 is intended to affect the input circuit of amplifier tube 23. This oscillator can be arranged to generate oscillations of uniform amplitude at a high frequency, generally much higher than audio frequencies. These waves can be modulated by the modulator 24, affected by the vibrations to be recorded; as, for example, by a, microphone 25.

The output circuit of tube 23 includes the transformer 26, the secondary coil 27 oi' which is connected across the members 17, 14. Included in this circuit is an impedance such as a resistance 8, acting as a ballast to prevent any corona illumination to exist between members 17 and 14, even when the modulations are of a large amplitude.

The guard field 18 is arranged to be in phase with the recording field. To effect this result, the oscillator 22 can be coupled as by a transformer 29 to the input circuit of the amplifier accesos tube 30. The secondary' coil 31 4of this transformer can be tuned as by the variable condenser 32, to the carrier wave frequency, whereby there is a further assurance that thecircuits respectively affecting the potential gradients forI the elds 15l and 18, are keptnon-interfering. 'Ihe output circuit of tube 30 includes the transformer 33, the secondary coil 34 of which is'connected across the guard electrode 19 and electrode 14 in order to provide the field 18.

'Ihe intensity of this guard field, as heretofore mentioned, is lbelow the ionization point for the gas or air separating the electrode structures 13 and 14; while the intense recording field, is strong enough due to its modulations, to produce ionization in this gas and therefore to produce the variable density record.

Other schemes for limting the maximum in: tensity of field 15 in place of the insertion of the series resistance 28 could be utilized. For ex- -ample, in the form of Fig. 3, there are electrode structures 13 and 14 similar to those of Fig. 1,` but the modulated high frequency alternating current is impressed across the guard electrode o structure 19 and the lower structure 14. An impedance, such as the coil 35, can .be inserted between the marking or recording electrode member 17 and the guard electrode member 19. Since the area of-the guard electrode member 19 is much greater than the recording edge of member 17, the relative intensities of the two fields are maintained.

In place of the coil 35, there is shown in Fig. 4 a corresponding impedance in the form of a condenser 36 for providing the same limiting effect as coil 35.

I claim:

1. Means for recording varying electric potentials on a sensitized surface, comprising means creating a recording electrostatic field acting on gas adjacent said surface over a limited portion thereof, and means for producing a guarding held surrounding said electrostatic field, of an intensity insufllcient to affect the surface.

2. Means for recording varying electric potentials on a sensitized surface, comprising means creating a recording electrostatic eld acting on gas adjacent said surface over a limited portion thereof, and means for producing a converging guarding eld surrounding said electrostatic field and of an intensity insufiicient to affect the surface.

3. Means for recording varying electrical potentials on -a sensitized surface, comprising fio iis

potential gradient of the recording field below the point of diffuse luminous discharge.

4. Means for recording varying electrical potentials on a sensitized surface, comprising means creating a recording electrostatic field acting across a gas adjacent said surface -and over a limited portion thereof, and means for producing a eld surrounding the recording field and in phase therewith, said surrounding field being of an intensity insuiiicient to affect the surface.

5., In a recorder using a carrier frequency, the combination of a recording electrode vstructure and another electrode structure between which structures a recording surface is passed, a third electrode structure surrounding said recording electrode, and electrical connections between said three electrodes to cause a carrier frequency electromotive force to be impressed across said recording electrode and said other electrode, and across said third electrode and said other electrode, thus providing two electrically parallel fields. and means to keep the frequency in each field in phase with the frequency in the other field.

6. The combination as dened in claim 5, in which the iield across the recording electrode and the other electrode is conned to a narrow area.

7. 'I he combination as dened in claim 5. with means for limiting the value of the field across the recording electrode and the other electrode below the corona point.

8. The combination as defined in claim 5, with means to impose on the carrier eld across the recording electrode and the other electrode a recording frequency without disturbing the field across the third electrode and the other electrode.

9. The process of recording potential fluctuations on a sensitized surface which comprises creating a normally diverging electrostatic recording field, and subsequently preventing said recording eld from diverging by surrounding said recording field by a converging non-recording eld.

10. The process of recording potential fluctuations on a sensitized surface which comprises creating a normally diverging electrostatic recording field, and subsequently causing said normally diverging electrostatic'feld to converge to a focus by surrounding said recording field by a converging non-recording eld.

11. The process of recording potential fluctuations on a sensitized surface which comprises creating a normally diverging electrostatic recording field, subsequently preventing said recording field from diverging by surrounding said recording field by a converging non-recording field, and varying said recording field without disturbing said non-recording field.

l2. The process of recording potential fluctuations on a sensitized surface which comprises creatitng a non-homogeneous electrostatic eld, a portion of which is intense enough to produce ions for recording, the remainder of the ield being less intense than is required to produce ions in the medium in which the lm is used, and directing said remainder to focus said intense portion to form an elemental image on said surface.

FRANK RIEBER.

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