US1718618A - Method and heans for recording sound waves - Google Patents

Description

J. L. \NALKER June 25, 1929,

METHOD AND MEANS FOR RECORDING SOUND WAVES Filed Dec. 1.9,

1924 4 Sheets-Sheet l June 25 1929. WALKER I 1.718.618

METHOD AND MEANS FOR RECORDING SOUND WAVES Filed Dec. 19, 1924 4 Sheets-Sheet 2 J16. Mi/fez' June 25, 1929.

METHOD AND MEANS FOR RECORDING SOUND WAVES Filed Dec. 1 1924 I 4 Sheets-Sheet 3 lulu-nu "1"111 J. 1.. WALKER 1318.618

June 25, 1929. J L, WA KER 1,718,618

METHOD AND MEANS FOR RECORDING SOUND WAVES Filed Dec. 19/ 1924 4 Sheets-Sheet 4 j y I J4.

Patented June 25, 1929.

UNITED STATES JACK L. WALKER, or DALLAS, TEXAS.

METHOD ANDIMEANS FOR RECORDING SOUND WAVES.

Application filed December 19, 1924. Serial No. 757,083.

This invention relates to new and useful improvements in method and means for recording sound waves.

The invention has to do with that class of sound recording and reproducing which in volves the use of photography and electricity, and in which the record is made on a sensitized film or strip.

The object of the invention is to improve the quality of the record by recording the sound variations in an accurate manner. A further and important object is to reduce to a minimum the tendency of the images photographed on the film, to pile up or overlap. An advantage gained is that even at comparatively high frequencies the variations of the sound waves will. be recorded distinctly.

Another object of the invention is to record images of varying density by modulating the volume of light rays acting upon the film, said modulation being controlled by sound waves. A still further object of the invention is to intensify the record by employing a transparent film and simultaneously recording variation of sound by controlling the volume of beams of light directed on each side of the film, through a stationary aperture or slit. An important object of the invention is to provide means for radiating and conducting 0 the heat generated by the light rays, so as to protect the film and at the same time to mask ofi? that portion of the film, which it is not desired to expose.

In carrying out the invention a powerful beam of light is directed on a restricted opening through which the film is exposed to the rays of light. The rays of light are concentrated about the opening from a source withina wide vertical angle and extending either above or below the horizontal. plane of the opening, thus being directed from comparatively wide angles. Means actuated by the sound waves is provided for varying the amplitude of the vertical angle of the source of r light, whereby the volume of light admitted to the film is controlled and the density of the images photographed, modulated in accordance with the variations of the sound waves. It is highly important that the opening be stationary with relation to the travel of i the film. Its height longitudinally of the film must be restricted to a minute degree so as to eliminate injury to the film from the heat generated by the light rays and also to permit a sensitive actuation of the controlling means, whereby a slight movement of the same Wlll vary the volume and density of the llght rays, to a marked degree, and the vibrations set up by the most delicate sound waves,

the film which are not to be exposed at the opening, are necessary, but permit of great varlatlon.

A construction designed to carry out the invention will be hereinafter described together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, in which an example of the inven-,

tion is shown and wherein:

Fig. 1 is an elevation of an apparatus constructed for carrying out my invention,

Fig. 2 is an enlarged end view of the film guide and shutter mechanism,

Fig. 3 is a cross sectional View on the line 33 of Fig. 2,

Fig. 4: is a cross sectional detail on theline 4-4 of Fig. 2,

Fig. 5 is an enlarged vertical view of the film guide and shutter mechanism, as in Fig. 1, with the guide insection,

Fig. 6 is a viewv of a record strip showing the recorded images of varying density,

Fig. 7 is a detail illustrating the beam of light which is photographed on the film,

Fig. 8 is a diagrammatical view illustrating a normal angle of illumination, and

Fig. 9 is a diagrammatical View illustrating an angle of illumination of reduced amplitude,

In the drawings the numeral 10 designates a base support having a film channel 11 extending therefrom. A top plate 12 is spaced above the support 10 by corner posts 13. The plate 12 is provided with a film guide slot 14: through which the film A, may pass. By the term film I mean any sensitized strip capable of recording 'photographically and in some instances being transparent.

In carrying out this method of recording sound waves, it is necessary that the film be amply protected from the heat of the light nel for the film extending from the slot 14. This housing overhangs an upright housing 16 mounted on the base 10 so as to guide the film into the guideway 11. Within the housing 15 I mount a pair of very thin metallic strips 17 of a resilient nature which project from the lower end of said housing to within a fraction of an inch of the top of the housing 16. This producesa slit transversely of the device which in actual practice may have a height of substantially one one-thousandth of an inch. It is necessary that this slit or aperture be extremely fine so as to admit but a limited portion of the rays of light concentrated therearound. It is to be understood that allot the apparatus herein described permits of a wide variation of construction and is specifically set forth merely to explain the invention.

On each side of the slit which we will designate by the character 18, I mount an elongated shutter blade 19. By employing the thin strips 17 and the narrow slit 18, the shutter blades may be disposed in close proximity to the film which passes down between said strips, the latter contacting with each side thereof, These strips also engage the sides of the films with sufiicient closeness to prevent fire creeping up into the housing 15. The blades have'their outer ends united so as to control the admission of light atthe edge of the film. This is also true at the inner ends of theblades where they are made integral with'an actuating lever 20. The lever has sufficient length to perform its function and'is pivoted at its outer end a bracket 21 which is mounted on a plate 22, having slots 23 for receiving the posts 13 .on one side of the device. The posts 13 on this side of the device are screw threaded and receive adjusting'nuts 24 between which the plate 22 is fastened. A similar but shorter plate 25 is disposed above the plate 22 and has slots 26 for receiving said posts. The plate 25 is fastened into position by adjusting nuts 27 mounted on said posts above and below the plate 25. I A suitable vibrating device 28 of the soundwaverecording type is carried by the plate 25 and is connected with a horn 29 for collecting the sound waves which act upon the diaphragm 0t thedevice 28. The diaphragm has connectionwiththe lever 20 in the usual manner as indicated'at 30. The .vibratlons caused by the sound waves may be I communicated to the lever 20 by electro-magneti'c means.

Itwilhbe seen that vibrations of the dia- .phragm will cause the lever 20 to swing thus moving the blades 19 in a vertical arc in ac- I In order thatthe shutter blades may. normally have their lower edges at the desired position, the

adjustment of the plates 22 and 25 is provided. By reason of the slots 23 and 26, said plates may be adjusted inwardly and outwardly with relation to the posts 13 and the position oi the connecting point 30 between the lever 20 and the vibrator may thus be changed to vary the amplitude of movement of the shutter blades 19. By adjusting the top plate 12' the strips 17 may be moved to vary the aperture 18.

It is understood that while I have shown single blades on each side of the aperture 18, it would be possible to use only one blade and photograph from one side only. It is to be understood that various means for modulating the light admitted through the aperture may be used and shutters oi various constructions are contemplated. It is pointed out that by employing a comparatively long lever 20, only a very slight movement contributed to the same by the sound vibrating means, will cause the blades to move to a much greater degree, thus recording the slightest ariations of the sound waves.

A powerful beam of light being focused or directed about the aperture 18, it is evident that the image of said beam will be photographed on the sensitized surface of the film. It is desirable to concentrate the beam of light in'nnediately around the aperture 18 so as not to waste any of the valuable rays, but to provide for an adjustment of the apertiure. It is to be understood that at no time is the aperture, 18 closed so as to eliminate the light rays therefrom. The function of the blade or shutter 19 is to modulate the volume of light and thus control the density of the image which is photog aphcd. By vertically moving the blade to obstruct the projection of some of the light rays acting upon the aperture the volume of light admitted to the film is reduced.

As an example of a source oi light it have shown an incandescent electric lamp 31 of high candle power, as it is desirable to use as strong a light as possible. This lamp is provided with a vertical filament which may extend above or below the horizontal plane of the aperture 18. It is to be understood that light may be concentrated upon the aperture within an are or angle of su stantially 180 degrees horizontally and vertically. The light derived from the source within 18-1) degrees horizontally, supplies the beam of light, the volume of which is decreased or increased within a radius of wide range vertically, by the movement of the shut ter blade. A concaved reflector 33 is lo cated at the proper distance from the lilament to receive and retract the reflected rays upon the filament in order to receive the hill benefit of the light; also to cast the rays of light through a condcnsing'lens 3i and focus the same around the aperture 18. Each lens is mountedin a frame carried by a bracket 36 on the outside of a fire partition 31', which latter has an opening through which the beam of light is projected.

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aperture 18 and the film.

The rays of light being directed from a source extending from above and below the horizontal plane of the aperture and from comparatively wide angles, will be diminished in volume as the blade is moved downwardly to eliminate a portion of the beam of light from impingement on the film. This is illustrated in Fig. 9, in which the blade 19 has been swung down far enough to mask off the rays of the upper portion of the beam of light and change the angle of illumination, thus reducing the volume of light admitted through the aperture 18 and photographing an image of less density. \Vhen the blade or shutter is swung upwardly as in Fig. 8, the volume of light admitted as well as the den sity of the image will be increased.

By placing the blade 19 in close proximity to the aperture 18 and the film, and disposing the source of a light at a point or points removed from the blade, a comparatively wide angle beam of light will be concentrated upon the aperture; consequently a slight movement of the blade will effect the rays of light of the beam to a considerable extent, said rays being admitted to the film under the lower edge of the blade. It will be seen that at no time are the rays entirely out off from the film and thus no transparent portions will be had on the record. The movements of the shutter being controlled entirely by the vibrations set up by the sound waves, it is evident that the images of light which are photographed on the film, will vary in density in accordance with said variations, whereby a record of the sound waves will be had.

Provision must be made for radiating the heat and conducting the same away from the Of course, the metal casings 15 and 16 and the strips 17 will radiate some of the heat and protect the film from the same. However, it is advisable to provide additional means, such as a fire shield which may include a. plurality of vanes 40 diverging toward the source of light from a common point of connection, which latter forms a barrier transversely of the light beam, the blade 19 being located relatively between two of these barriers so that only the desirable portions of the light beam pass through to the blade and aperture 18. These barriers serve to mask oil the rays from the upper portion of the shutter, thus permitting the shielded portion of the shutter to radiate the heat. By making the vanes 40 of good heat conducting material, such as copper or other material or by interposing vacuum cells therebetween, the heat waves will be dissipated and the blade and component parts maintained comparatively cool. The best results are had by leaving the outer ends of the blades free from contact with other parts. It is to be understood that any suitable means for conducting the heat away from the film, may be employed.

The minute aperture or opening is of vast importance not only because it reduces to a minimum the area of the film exposed to the heat generated by the rays of light, but for other reasons. The heat generated by the concentrated rays of light projected from a one thousand candle power lamp through a condensing lens, would be intense enough to ignite and destroy the film. The speed of travel of the film and the size of the exposing aperture, lengthwise of the film, absolutely control the fineness of tone and quality of the record, particularly so far as the spacing apart of the images which record the sound waves are concerned. It the speed of travel of the film is too slow, even with a minute aperture, a certain amount of overlapping of the images will occur. This overlapping causes a blurring of the images and a discordant reproduction of the sound waves instead of a sharp and distinct demarcation therebetween or aproper blending of the same. The overlap must be reduced to a minimum and is best accomplished by running the film at a high rate of speed.

lVhile it would be possible to reduce the aperture 18 transversely of the film so as to record the light images along the margin of the same film upon which moving pictures are taken and thus synchronize the sound waves with the picture, it is more satisfactory to record the sound wave images on a separate film or strip, traversed at the same speed ratio as the picture taking film. The aperture may thus extend the width of the film or a portion thereof, and while it may vary in shape, an aperture at right angles to the edge of the film is preferable.

I have illustrated light sources on each side of the film and by use of two beams of light, images of still greater density are had. The use of beams of light on both sides of the film increases the density of light directed upon the film and the second shutter blade gives a greater control of the rays of light whereby the recording of the sound waves is amplified.

The double exposure at opposite sides of the film functions to increase the speed at which it is possible to record sound waves photographically as well as to amplify there by the modulation of said waves. It also acts to secure a more even distribution of the light acting upon the film whereby a perfect exposure is made, as it permits the use of a smaller aperture by doubling the amount of light that it is ordinarily possible to put on a film, thus making the vibrations more sharp and free from overlap. Another important advantage is the even distribution of heat upon the film by applying the light at both sides and renders possible the use of heat filters as there is sulficient light for proper exposure even with the loss occasioned thereby. The celluloid film used in motion picture photography has a certain thickness and if a certain number of heat units are used to record the sound upon the film, it is desirable to divide these units and make each side of the film bear the burden of absorbing them. Celluloid being a poor conductor of heat is slow to dissipate the heat and if a too large number of heat units are used upon one side of the film during the maximum opening of the shutter damage or fire is liable to occur.

The film is, of course, developed and fixed in the usual manner and reproductions made therefrom. There are many ways of reproducing the sound waves, the most popular of which is projecting a beam of light through the film similar to the manner of recording, herein described, and substituting for the lamp and condenser on one side, a selenium cell to collect the rays of light coming through the aperture and the film. The said selenium cell being electrically connected to a suitable apparatus for producing sound. Means other than a selenium cell may be used as is well known in the art.

It is pointed out that the shutter blade 19 being disposed immediately above the aperture and the rays of light being directed thereupon, said shutter will normally cut off some of the rays of light directed upon the aperture, thus maintaining a normal angle of illumination. The amplitude of the area of illumination may be varied and consequently the voliune of light admitted through the aperture is controlled by the upward and downward movement of said shutter. It is preferable to limit the downward stroke of the shutter so that its lower edge does not overlap the aperture or close oil any portion thereof. However, this is not absolutely necessary under certain conditions. The shutter should be made of a suitable material which will be light in weight and capable of standing intense heat. Satisfactory result-s have been had from the use of aluminum, but other materials may be used.

Referring again to the normal degree of the angle of illumination established by the stationary position of the shutter when the same is at rest, it is pointed out that this angle may be varied by adjusting the plates 22 and 25 so as to raise or lower the lever 20 and the blades 19. By lowering these parts, the normal angle of illumination would be reduced and by elevating the same the normal angle of illumination would be increased. This is important and necessary in order that the proper exposure may be made in accordance with the speed of the film in order to prevent over or under exposures.

While it is desirable to use a condensing lens in connection with the apparatus, it is possible to obtain good results by emitting a condensing lens and merely concentrating rays of light of sufficient intensity about the aperture 18. These rays of light may be derived from sources within a wide angle not comparatively close to the shutter so as to obtain the advantage of the concentration of the same, or in any other suitable way.

In contradistinction to a shutter which is located relatively at a distance from the film, it is obvious that by locating the shutter in close proximity to the film, the spreading of the rays of light controlled by the shutter is reduced to a minimum and this is a very important feature as it enables the use of the rays of light which are controlled by the operation of the shutter in accordance with the variations of the sound waves.

An additional advantage gained by placing the shutter blade in close proximity to the aperture and the film and uniting the ends of the blades so as to control the admission of light through the ends of the aperture as wel through the sides thereof, is that rays of light may be concentrated from a source within an arc of 180 degrees horizontally on each side of the film. This permits the loca tion of powerful sources of light close up to the shutter and the film, which would not be possible if the shutter is located at a distance from the aperture and the film.

ii hat I claim, is: v

1. The method of recording sound waves which consists in photographically recording on a sensitized film rays of light directed on each side of said film, and modulating the density of the light rays in accordance with the variations of the sound waves.

The method of recording sound waves which consists in photographically record ing, simultaneously upon a. sensitized film rays of light directed from both sides of said film and admitted through minute relatively statioi'iary openings, and modulz'iting the density of the rays of light in accordance with the variations of the sound waves.

3. The method of recording sound waves which consists in photographically recording light rays from both sides of a sensitized film, said light rays being admitted through minute relatively stationary openings, and obstructing the direct projection upon the film of portions of the light rays by means adjacent the film and controlled by the variations of the sound waves.

l. The method of recording sound waves which consists in photographically recording upon a sensitized film the radiant rays of light admitted through a relatively stationary minute opening, modulating the density of the photographed rays in accordance with the variations of the sound we es, and mashing oil the film except at the opening by meai'is capable of rapidly conducting the heat away from the film.

5. The method of recording sound waves which consists in photographically recording upon a sensitized film images of light rays admitted through a minute opening from a light source extending above or below the horizontal plane of the opening, and controlling the volume of said admitted rays adjacent the film by the variation of, the sound waves.

6. The method of recording sound Waves which consists in photographically recording upon a sensitized fihn, rays of light concentrated upon the film from within a comparatively wide angle, and obstructing a portion of said .rays within said angle by means actuated by the sound variations.

7. The method of recording sound waves which consists in photographically recording upon a sensitized film images of a light source within an arc of substantially 180 degrees horizontally, varying the volume of light by utilizing portions of the light rays within a vertical arc, and controlling said variations by means of the sound waves.

8. The combination of a source of light rays, a film guide having a minute aperture for exposing the film, and a shutter co-acting with the aperture in close proximity to the film to modulate the light rays and produce an image of varying densities, sound controlled means for adjusting the shutter, whereby light rays within a vertical area may be utilized and a maximum variation of such area controlled by a minimum movement of the shutter.

9. Means for photographically recording sound waves on a sensitized film through a minute aperture, including a source of light rays, and a movable element for controlling the volume of light passing through the aperture to the film, acting to modulate the light rays at the aperture to regulate the amount of exposure relative to the speed of the film to produce images of varying densities thereon.

10. The combination with a source of light rays, of a photo-sensitive surface, means for exposing said surface through a minute opening, and means disposed in close proximity to said surface and said opening for controlling the volume of said rays reaching said surface at difierent points longitudinally of said surface by and in accordance with sound waves, whereby a record varying in density longitudinally will be produced.

11. The combination with a source of light rays, of a photo-sensitive film, means for exposing said film through a minute opening, a shutter controlled by sound waves for controlling the volume of light rays admitted through the opening, and radiating means intercepting the outer light rays for shielding the upper portion of the shutter from the heat rays of the light, the shielded portion of the shutter acting to radiate heat.

12. The combination with a source of light rays, of a photo-sensitive film, means for exposing said film through a minute opening, acting to rapidly conduct heat away from the opening, a shutter controlled by sound waves for controlling the light rays admitted through the opening, and means for shielding the upper portion of the shutter from the heat rays of the light, the shielded portion of the shutter acting to radiate heat.

13. A shutter for controlling the admission of a powerful beam of light to a sensitized film through a minute opening, comprising a radiating body having its lower portion exposed to the light beam and its upper portion shielded from the beam of light, whereby its upper portion acts to radiate heat and prevents excessive temperature of its lower portion.

14. The combination of a film guide having a minute transverse opening, a film travelling through said guide having both sides exposed by said opening, light sources directing rays of light upon the openings on each side, and shutters controlled by sound waves for regulating the volume of light admitted to each side of the film through each side of the opening.

15. The combination of a film guide having a minute transverse opening, a film travelling through said guide having both sides exposed by said opening, light sources directing rays of light upon the opening on each side, and shutters controlled by sound waves for regulating the volume of light admitted. to each side of the film through each side of theopenings and havin shielded portions for rapidly conducting the heat away from the opening.

16. The combination of a film guide having a minute transverse opening, a film travelling through said guide having both sides exposed by said opening, light sources directing rays of light upon the openings on each side, and shutters controlled by sound waves for regulating the volume of light admitted to each side of the film through each side of the opening, and means for shielding the shutters and the film guide from heat waves.

17. The combination with a film exposure controlling shutter operated by sound Waves and a source of light directed toward said shutter, of means for masking oil the light from the upper portion of the shutter com- "prising a shield having a plurality of vanes radiating toward the source of light.

18. Means for recording sound waves JACK L. WALKER.

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