US2037739A - Method and apparatus for recording and reproducing sound - Google Patents

Description

Filed Feb. 13, 1955 2 Sheets-Sheet l "gm LOUD g: 2 SPEAKER AMPLIFIER ,3 2 f INVENTOR 5 E l D i o 22 faul Safransfm D E 2 BY p D EC, n 22D %//,a1y,%$-bm e: in: o Efcs ATTORNEYS METHOD AND APPARATUS FOR RECORDING AND REPRODUCING SOUND Filed Feb. 13,. 1933 2 Sheets-Sheet 2 ATTORNEYS Paul fiafran "in; BY 0 Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE METHOD AND APARATUS FOR RECORDING AND REPRODUCING SOUND Paul Safranski, New

York, N. Y., assignor to 17 Claims.

This invention deals with the photographic recording of sound and. with the reproduction of sound from a photographic film record thereof.

One of the objects of this invention is to provide a practical and thoroughly dependable method and apparatus for recording sound on a film and for reproducing photographic records of sound. Another object is to provide a method and apparatus of the above-mentioned character in which the efficiency of heretofore known methods and apparatus is greatly increased, in which substantial and far-reaching economies in energy consumption may be inexpensively effected, and in which uniformity of intensity of lo sound over the necessary wide range of frequencies may be dependably achieved.

Another object is to provide a method and apparatus of the above-mentioned nature in which costs of operation and maintenance are greatly decreased and in which the high operating skill, necessary in the satisfactory maintenance and operation of heretofore known apparatus, may be successfully dispensed with. Another object is to provide a method and apparatus of the above-mentioned character in which critical adjustments and critically sensitive devices or parts are dispensed with, and to provide, particularly as to the apparatus for sound reproduction an apparatus of high economy of operation and so simple in construction and control that it is virtually fool-proof and virtually ideally suited for use in homes, schools, and the like,

Where its operation and control must necessarily be by unskilled operators.

35 Another object is to provide a method and apparatus for sound reproduction that lends itself readily to low cost of production and to low cost of maintenance. Another object is to provide a sound reproducing method and apparatus 40 that will respond to and reproduce, with substantial uniformity, frequencies over such a wide range that defects, such as are present in present-day apparatus, in the ultimate sound, are eliminated and thus naturalness or virtually perfect reproduction achieved. It is in particular an object of this invention to provide a sound reproducing system of this last-mentioned character for use in large auditoriums, such as theatres, halls, or the like, where the intensity or volume of sound must necessarily be very great and where,

because of such magnitude of volume, apparently slight imperfections are magnified and more easily detectable.

Another object is to provide a system and apparatus for sound reproduction in which the output of the photoelectric cell or other light-sensitive device per unit of light input (at the initial source of light) is high, and thereby to lessen energy consumption, diminish the amplification necessary, and insure longer life and low cost of operation.

Another object of this invention is to provide a light or optical system to which the film record and the light-sensitive or photoelectric cell may be subjected that will maintain substantial uniformity of frequency response over ranges on the order of from 55 cycles per second to or above 8000 cycles per second. Another object is to provide a sound reproducing method and apparatus in which sound-frequency-components of very low and of very high frequencies are faithfully reproduced and thus the true quality or naturalness of the recorded sound reproduced.

Another object of this invention is to provide a method and apparatus of the above-mentioned character in which the many undesirable and detrimental factors inherent in present-day apparatus of this character may be successfully eliminated; among these factors may be mentioned the expense of construction and maintenance of the slit through which the light is made to impinge upon the film, the precision and accuracy of adjustment of the slit and the maintenance of this adjustment, the difiiculty and necessity of keeping this extremely minute slit clean and free from foreign matter, moisture, oil, oil vapors, and the like, the sensitiveness of adjustment of the component parts of the optical system, the low efficiency, the high cost of supervision and maintenance, the high energy consumption, and like factors. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated inthe following claims.

In the accompanying drawings, in which are shown, by way of illustration, several possible embodiments of certain of the mechanical features of my invention,

Figure 1 is a side elevation of the assembled apparatus for sound reproduction;

Figure 2 is a vertical cylindrical sectional view on an enlarged scale of what may be termed the optical system of the apparatus of Figure 1;

Figure 3 is a vertical transverse sectional view as seen on the line 33 of Figure 2;

Figure 4 is a schematic or diagrammatic plan View of the apparatus of Figure 1, certain additional parts being indicated diagrammatically;

Figure 5 is a fragmentary portion of a standard motion picture film showing diagrammatically the sound track thereon with one kind or type of sound recording;

Figure 6 is a plan view of a fragment of standard motion picture film showing diagrammatically the sound track thereon with another kind or type of sound recording;

Figure '7 is a side elevation, as seen from the left, on an enlarged scale of the photoelectric cell of Figures 1 and 4;

Figure 8 is a perspective view of a light ray controlling element of the optical system; Figure 8a is a top plan view thereof; Figure 8b is a front elevation thereof; Figure 8c is an end elevation as seen from the left of Figure 8b, and Figure 8d is a central horizontal sectional view as seen on the line 8d8d of Figure 82).

Figure 9a is a top plan view, and Figure 9b is a front elevation of a modified form of light ray controlling element, and Figure 9c is an end elevation thereof as seen from the left of Figure 92);

Figure 10a is a front elevation, and Figure 10b is a top plan view of another modified form of light ray controlling element, and Figure is an end elevation as seen from the left of Figure 10a;

Figure 11 is a perspective view of another form of light ray controlling element, and Figure 11a is a top plan view thereof, Figure 111) being a front elevation thereof, and Figure being a side elevation as viewed from the left in Figure 111); and

Figure 12 is a diagrammatic representation of a possible form of sound recording system and apparatus embodying my invention.

Similar reference characters refer to similar parts throughout the several views of the drawmgs.

As conducive to a clearer understanding of certain features of my invention, I wish first to point out that I may first produce, in any suitable manner, a sound record on a photographic film and in Figures 5 and 6 I have shown fragments of motion picture films with sound tracks and sound records thereon of a character now in practical use. Referring first to Figure 5, I have shown a section of motion picture film l0 preferably of standard size and provided with socalled frames H on which appear the scene or scenes that have been photographed and alongside of the frames I I is a relatively narrow band portion called the sound track; this portion or sound track is indicated at [2 and in practice is about one-eighth of an inch in width. The film I0 is provided with the usual apertures l3 to coact with the teeth of suitable sprocket wheels and the like for running the film for motion picture projection and sound reproducing purposes.

The sound track l2 of Figure 5 bears, as is diagrammatically indicated in that figure, the sound record which, with the system of sound recording that results in this kind of sound record, consists of so-called lines extending transversely of the sound track, all of the same length, but of variable or varying density, the density varying in effect with the variation in frequency of the recorded sound. This varying density is indicated in Figure 5 by the varying shading of these transverse lines. A beam of light, projected through the sound track as the film is moved in the direction of its length, thus varies in intensity at an audio frequency rate and more particularly in accordance with the frequency of the sound that is recorded on the sound track.

In Figure 6 I have shown diagrammatically the same film ill but with a sound track i4, also of a width of about one-eighth of an inch, bearing a sound record in which the light-passing quality of those portions of the film bearing the sound record is constant but an audio frequency variation in the amount of light passed through the entire sound track is achieved by varying, at the audio frequency rate, the width of the actual sound record; this is clearly indicated on the sound track M of the. film H) of Figure 6.

The method and apparatus for sound reproduction of my invention are particularly adapted for the translation of sound records like those above described into sound, and accordingly I provide an arrangement for guiding and moving the film [0 (Figure 1) the latter being moved preferably at a constant rate of speed.

Any suitable form of guiding arrangement or so-called film gate may be employed for fixing the path of movement of the film I!) as the latter is moved, preferably in a downward direction, between and over the sprocket wheels l5 and 16 which may be driven in any suitable manner and at the desired speed and intended uniform rate; where my apparatus is associated with a motion picture projecting machine, the driving mechanism l5l6 may be actuated in any suitable manner from the apparatus that moves the film for projecting purposes, suitable 1 provision being made to achieve continuity of movement of the film I0 along the above-mentioned path as distinguished from the intermittent movement of the film for picture projecting purposes. The film gate or guide is generally indicated in Figure 1 at 17 and it serves, as above noted, to fix the plane in which that portion of the film ID that is between the sprockets l5l 6 moves; the film gate l! is provided with a suitable aperture l8 of substantial dimensions so as not to obstruct or interfere with the beam of light that is to be passed through the sound track of the moving film.

To the right of the thus-apertured film gate or guide I! is positioned and suitably mounted a suitable light-sensitive device preferably taking the form of a photoelectric cell generally indicated in Figure l at 19. The photoelectric cell includes a suitable glass envelope in which are mounted the electrodes; the electrodes include a plate member 29 of suitably treated sheet metal which is given the shape, as is better shown in Figure 4, of a half cylinder and positioned substantially at its axis is the coacting electrode in the form of a smaller-diametered rod or cylinder 2| (Figures 1 and 4). These electrodes are supported in any suitable manner and are connected to terminal conductors 22 and 23 in any suitable way. The concave face of the electrode 20 faces toward the film guide I! and its midpoint, as viewed from the left in Figure 1, is substantially on the optical axis AA with respect to which also the sound track on the film I0 is centered.

The plate 20 of the cell I9 is thus positioned in the path of the beam of light, more clearly hereinafter described, that passes through the sound track of the film l0 and emerges through the large apertures it by which the beam is not affected; the intensity of the light beam, it might at this point be noted, is varied by the sound record on the film H] (see the sound track l2 or the sound track M of Figures 5 and 6, respectively) and thus the intensity or quantity of light striking the light-sensitive electrode is varied so as to in turn vary the electrical conductivity of the cell l9, thus to achieve in the output circuit of the latter a corresponding audio frequency current.

In Figure 4 the output circuit of the cell I9 is diagrammatically represented and it includes a suitable source of current 24 of suitable potential, a suitable amplifier, preferably of the thermionic type, generally indicated at 25. Thus, the energy in the output circuit in which the cell I9 is included is amplified and the output of the amplifier 25 is in turn fed to a suitable translating device, such as a loud speaker 26 indicated diagrammatically in Figure 4. The loud speaker 26 may be of any suitable form or construction. Where the apparatus is intended to be used in large auditoriums, such as motion picture theatres, for example, the volume of the sound ultimately produced by the loud speaker 26 is substantial in magnitude and, if naturalness and true quality of the recorded sound are to be achieved, the amplifier must have supplied to it, by the circuit of the photoelectric cell l9, audio frequency currents which must be made up of the same frequency components recorded on the film and these components must, in intensity, be of magnitudes corresponding, without variation as frequency changes, to the respective magnitudes thereof recorded on the film.

The film guiding and driving mechanism and the support for the photoelectric cell I9, referring now to Figure 1, may be related in any suitable manner to a suitable frame or support, a portion of which is shown at 21; part 21 may be considered as part of a motion picture projecting machine. At the left-hand end of the frame or support 21 I provide a socket 28 for the reception of a lamp bulb 29 of the incandescent filament type, which I prefer to use as a source of light. The socket 28 is preferably adjustably mounted in any suitable way preferably so that different styles or types of bulbs may be more readily related to the optical systern and remaining parts. The adjustable mounting of the socket 28 may be of any desired character and by way of illustration I have shown the socket 28 mounted to be capable of adjustment in three directions, namely, vertically, horizontally (to the left or right as viewed in Figure 1) and horizontally but at 90 to the justmentioned horizontal adjustment.

Thus, the socket 213 may be carried on an arm 36 slidably supported in a block 3|, movement of the socket Z8 and the arm 30 to the left or right being controlled by a suitable thumb nut 32.

The block 3 I, however, is slidably supported on an upstanding post 33 and it may be raised or lowered along the post 33 by the thumb nut 34, thus to raise or lower the lamp 29.

The post 33 is supported in a slide 35 guided in ways 36 carried by the frame 21, the ways 36 extending at right angles to the plane of the sheet on which Figure 1 appears, thus to permit the lamp 29 to be moved toward or away from the observer viewing Figure 1. An adjusting screw 35 controls the position of slide 25.

The frame 21 is provided with an upstanding post 3 positioned intermediate of the lamp 29 and the path of the film l0, and post 31 is provided with a split clamping collar 38, the clamping action of which is controlled by the clamping screw 39. The clamping collar 38 supports the housing 40, preferably tubular in cross-section (with which the light ray controlling elements and lens or lenses are related and in which they are preferably sealed against moisture, vapors, foreign matter, and the like. The housing 40, moreover, is held by the supporting post 31 so that the axis of the tube 49 coincides virtually with the optical axis A-A above-mentioned and along which the sound track and the electrode 26 of the light-sensitive cell are alined.

Before considering in detail the light ray controlling elements related to the housing 43, it might first be pointed out that the lamp socket 28, with a lamp bulb 29 therein, is adjusted so that the center of the luminous mass of the filament at least approximately coincides with the optical axis AA and so that that center is spaced to the left of the housing 48 by a certain approximate distance. This coincidence and this distance need not be absolute; that is to say, though there is a preferred or optimum relation for a given incandescent filament bulb and hence a given position for the socket 28, both of which may be achieved by the adjustments of the lamp socket 23 as above described, relatively wide departures from this optimum position or distance are permissible, as will be pointed out in detail hereinafter. Suffice it at this point to note that a given adjustment for a given lamp bulb of one type will sufiice once and for all for subsequent lamps of the same type, the optical system forming part of my invention taking care of even the relatively wide variations in dimensions and shape of bulbs of a given type and intended to be uniform or standard throughout. In fact, far wider departures than just these manufacturing tolerances are permissible with the apparatus of my invention without requiring readjustment of the lamp bulb each time.

I might also note at this point that the shape, dimensions, configuration and structure of the filament itself may vary throughout very wide limits without affecting the performance of the system and apparatus. For example, it is not vital that a filament of carefully dimensioned rectilinear shape be employed as has heretofore been proposed in order to obtain a cross-section of beam at the intersection thereof with the sound track that is or approximates a straight line and is of minute thickness; the filament can be in the form of a ribbon extending generally parallel to one of the sound marks on the sound track (see Figures 5 and 6), or the filament may be a helix whose axis is thus substantially parallel to one of the sound record elements on the sound track, or the filament might be in the shape of an inverted V the plane of which extends at right angles to the optical axis A-A, or the filament might be of the concentrated filament type wherein, to all intents and purposes, the incandescent filament represents and virtually is equivalent to an enlarged point or sphere-like mass of light; these are several of the various possible forms or shapes of filament which, due to certain other features of my invention, I am enabled to employ.

Referring now to Figure 2 I have there shown on an enlarged scale the tubular housing 40 above-mentioned in connection with Figure 1. The left-hand end of the tube 1E which illustratively has an inside diameter of approximately 0.75", is counter-bored and threaded as at w in order that a disk-like element X may be fitted into that end of the tube 4!! and abutted against the shoulder 46 element X being held in place by a collar 4| threaded into the threaded counterbore 40 Interposed, however, between the element X and the collar 4| is a ring as and a plain glass disk-like window 43, the parts being sealed, in a manner hereinafter described, so as to exclude from access to the element X foreign matter, moisture, cil, vapors, and the like.

In so far as element X is concerned, it may assume various possible forms of which one form is shown in perspective in Figure 8.

Referring therefore to Figure 8, element X is made of glass, illustratively of crown glass having an average index of refraction of 1.52 and a dispersion factor for the D-line of 64.0 and is of a diameter adequate to be snugly received within the counter-bored portion 41% of the tube 40 (see Figure 2); this diameter may be on the order of On its right-hand face, as viewed in Figures 2, 8, and 8c, the element X is concaved to provide a cylindrical surface M the axis of which extends parallel to an element of the sound record (see Figures 5 and 6) and crosswise of the axis A-A (Figures 1 and 4). The radius of curvature of the cylindrical surface 54 is 0.125.

The left-hand face of element X, as viewed in Figures 2, 8, and 8c, is preferably curved and preferably is given the shape of a portion of a cylinder, the axis of which, however, extends 90 to the axis of the cylindrical surface 4 that is, referring to Figure 8, if the axis of cylindrical surface be considered as extending horizontally (in perspective), the axis of the cylindrical surface 55 is vertical. This relation appears more clearly from a consideration of Figures 8a, 8b, 8c, and 811. Its radius of curvature is 0.75".

On the right-hand face of element X (Figures 8 and 80) there remain segmental areas 45 and ll which are preferably though not necessarily covered with any suitable opaque material, conveniently by painting these surfaces with any suitable opaque paint, varnish, shellac, or the like.

The action of the element X will be described in detail hereinafter.

At the right-hand end of tube 48 (see Figure .2), the tube is interiorly threaded as at iil to receive an extension member 38 which exteriorly appears substantially conical but which interiorly is virtually an extension along the optical axis A-A of the tubular housing 4-3. The parts 48 and are interconnected by threads and sealed as hereinafter described.

The member at is bored out to provide cylindrical interiors 18 and 48 of progressively smaller diameters and supports a suitable lens or lenses which preferably take the form of achromatic: doublets.

Thus, a composite lens its-53 is seated in the cylindrical interior portion 48 and is held up against the right-hand shouldered end thereof by a ring 5i threaded into the part W and with the lens 49-50 sealed, as hereinafter described, to the part 18.

Seated against the left-hand shouldered end of the smaller cylindrical portion 43 is a composite lens 53-54, also sealed to the part and interlocked with the latter by spinning the edge 48 thereof over the right-hand face of the component lens 54.

The foremost or front achromatic lens 53-54 is made of flint glass having an average index of refraction of 1.52 and a dispersion factor for the D-line of'36.5. Its components are shaped as followsz-Component 53 is a double convex lens whose surfaces have radii of curvature of 6 mm. the component 54 is double concave and its lefthand face (Figure 2) has a radius of curvature of 6 mm. and its right-hand or front face has a radius of curvature of 17.5 mm.

Achromatic lens 49-59 is made of similar flint giass and its components are as follows:-Lens component 43 is a double convex lens having a radius of curvature for both of its faces of 9 111111.; lens component 50 is a piano-concave lens whose left-hand face has a radius of curvature of 9 mm. and whose right-hand face is plane. The diameter of lens 49-50 is A" and the diameter of lens 53-54 is 1 5", the diameters of the parts 48 and 68 of the member 48 being correspondingly proportioned in order snugly to receive the respective lenses.

Intermediate of the ends of the tubular ma. ber 45 (Figure 2) is mounted a diaphragm 55 which, like the various above-mentioned threaded members, may be made of metal; the diaphragm 55 is suitably fixed within the tube ll and it has a centrally positioned aperture 55 (see also Figure 3) which is square, being, with respect to the above-mentioned dimensions, in length per side.

The above-described parts thus related to the tubular housing 68 are related to the lamp bulb and to the film Ill and to the photoelectric cell !3 as is diagrammatically or schematically shown in 4 but, with respect to the dimensions above set forth, the following relations should be borne in mind:-

The distance 3 (Figure 4) from the filament ze of the lamp bulb 29 to the left-hand or rear face of the element X, where the filament '29 is illustratively a helix which is 0.375 in length and having an outside diameter of is approximately 1.25.

The distance C from the right-hand face of lens 53-54 to the right-hand face of element X is 2.875".

The distance D from the right-hand face of lens 53-55 to the diaphragm 55 is A The lenses 49-59 and 55-54 are relatively close together, approximately A and with a spacing (Figure 4) between the righ -hand face of lens 53-54 and the film Ii] of 0.375, film iii and hence the sound track lie at the focus of the objective lens system which these lenses form.

The distance F between the plane of the film iii and the vertical axis of the half--cylindrical plate 23 (where the latter has a radius of 0.375) is approximately 1.625.

I have above set forth somewhat in detail the physical dimensions and characteristics of the various parts of an illustrative embodiment of sound reproducing apparatus in order that their construction and action may be more readily carried out in practice, but it is to be understood that I do not desire or intend to be limited or restricted to these somewhat detailed structural relations. As for the action of the system and apparatus, I direct attention to the following:- Ii have hereinabove set forth by way of illustration various shapes and structures which the filament 29 of the lamp 129 of Figure 4 may assume; virtually, no matter what the shape of the initial or immediate source of light, the element X, when shaped substantially as described above, has the property of so refracting, reflecting, or otherwise affecting or controlling the light cylindrical surf ace rays emanating from that source as to Vastly elongate its shape in the direction of the axis of the cylindrical surface A l (Figures 2 or 8) on its right-hand or front face and to diminish, and to make uniform throughout this elongation, the vertical dimension thereof. For example, if the filament were concentrated or made short so that it represented virtually a disk of luminosity or incandescence or light of a diameter, let us say of a s" or element X, treating that disklike part as an object, transforms it into a tramversely elongated and vertically condensed concentration of light, thus forming virtually a secondary light source; moreover, though the shape of the initial luminous object was irregular or circular, the secondary source of light which ele ment X forms out of it, as just described, is virtually of uniform vertical dimension as that secondary source is viewed along the optical axis AA from the right toward the left (Figures 1, 2 or l). Illustratively, this concentration of light rays thus effected by the element X and when thus viewed extends entirely across the cylindrical face 44 along an element thereof and hence parallel to the axis thereof, and its vertical dimension is very minute, being on the order of ea or less, depending upon the distance B of Figure 4.

So effective is theaction of element X that, if filament 29 of the lamp bulb 29 is V-shaped with the plane of the filament extending transversely of the axis A-A, element X nevertheless so controls and affects the light rays emanating therefrom that the decrease in vertical dimension of the V of the filament and its elongation transversely are such that it is virtually impossible to discern from an examination of the thus-formed secondary source of light that the primary source of light actually is V-shaped.

The curvature of the cylindrical face 45 of the element X is such as to prevent a too great elongation in a direction parallel to the axis of the M in order thus to insure a high intensity of light per unit area of shape of the secondary li 'it source thus formed.

In any case, there is thus presented to the projecting lenses ii--53 and 53-5 5 and to the diaphragm 55 positioned in advance of the projecting lenses, what might be termed a luminous mass of ribbon-like shape extending horizontally across the optical axis AA and thus parallel to the individual portions of the sound track that make up the sound record on the film; the shape of this luminous mass is throughout a wide range virtually unaffected by the shape of the primary or incandescent mass and it forms what I term for convenience a secondary source of light. This secondary source of light forms the object which is projected by the lens or lenses carried in the member 33 (Figure 2) and by the diaphram 54 and there emanates from these lenses fill-5E and iiii5 l a beam of light which intersects the sound track (track l2 of Figure 5 or track 54 of Figure 6) in what is virtually a line having a length substantially equivalent to the width of the sound track and having a thickness as small as less than 0.001.

Accompanying the above action, however, there is another action Which results from an action by the element X whereby the latter forms what I term for convenience a tertiary source of light. Element X, aside from producing the above-mentioned luminous mass or secondary source of light, functions also to produce a general illumination of the interior of the tube to (see Figure 2) in that light rays from the primary source of illumination are passed through the element X and into the tube ill wholly aside from or in coaction with the illumination within the tube 40 achieved by the above-mentioned luminous mass or secondary source of light. The secondary source of light may be considered as superimposed upon or encompassed within the tertiary source of light; the former is of relatively high intensity and the latter is of lesser intensity per unit area but is of much larger area, its area being represented by the projected area of the cylindrical surface 44 of element X as the latter is viewed from the right in Figure 2.

Light rays from this tertiary source thus formed (including or supplemented by light rays from the secondary source) may be considered as diffused into or as extending more or less uncontrolled into the tube 40 (Figure 2) but as its light rays pass toward the right, diaphragm 55, positioned substantially at the left-hand focal point of the projecting lens or lenses 4950 and 5354, functions to determine the cross-sectional dimension of the beam of light which emanates from this tertiary source, giving it, due to the square aperture 55" (Figure 3) a square crosssection. The thus square-cross-sectioned beam may now be considered as the object so to speak which the projecting lenses 49-50 and 5354 project onto the plate 20 of the photoelectric cell 9.

These lenses first converge this square-crosssectioned beam of light from the tertiary source to the right-hand focal point of the lenses (coincident with the plane of the film If), Figures 1 and 4) whereupon the beam is diverged, being projected onto the plate 26 into a very greatly enlarged square or rectangular area which in Figure 7 I have indicated in broken lines at 52. The lenses, however, at the same time converge the light rays from the secondary source of light as already above described to the same focal point, the beams from both the so-called secondary source and from the so-called tertiary source being coincidently converged at the same focus (in the plane of the film) to intersect the film in the line above-mentioned in connection with the action of the lenses on the secondary source of light; I have been able to achieve a thickness of beam where the latter intersects the film and passes through it of as small as of 0.001".

The two beams are diversed onto the electrode 29 of the photoelectric cell [9 to illuminate the plate (disregarding for the moment any opaqueness or approach to opaqueness in the sound rack) in the large rectangular or square area 52 of Figure 7, thus achieving a far greater area of illumination of the light-sensitive surface and a far greater intensity of illumination thereof than has heretofore been achieved, with results of farreaching importance. Among the latter may at this point be noted the fact that the photoelectric cell is thus caused to function at a higher standard of operation and to have a far greater average current output in its output circuit than was heretofore possible.

As now the film lil is moved as above described, the individual bar-like portions or members of the sound track on the film I (see Figures and 6), varying in their dimensions or spacings or light-transmitting property (according to the method employed in making the sound record) correspondingly change the amount of light striking the plate ill (Figure '7) within the rectangular area 52 and correspondingly change or vary the flow of current in the output circuit (Figure 4) of the photoelectric cell l9 and correspondingly vary the energy input to the amplifier 25; the output of the amplifier 25 correspondingly varies and thus sufficient energy is available to actuate the loud speaker 25 at the desired intensit l vith my system and apparatus, however, 'as above described, I have found that I am enabled far to surpass the performance both as to quality and efficiency and in other respects heretofore known apparatus for sound reproduction. For example, I am enabled to achieve substantially uniform response in the photoelectric cell circuit or in subsequent circuits to all frequencies within a range from as low as 50 cycles per second to as high as 8000 cycles per second. It has heretofore been impossible to achieve this important characteristic and in known apparatus, the response throughout the middle portion of the above-mentioned range is substantially uniform but falls off rapidly and detrimentally not,merely at the extreme ends of this range but also throughout substantial end portions as the extreme limits abovementioned are approached.

The importance of uniform frequency response is very great; uniform frequency response means perfect faithfulness of reproduction and absolutely naturalness of ultimate tonal character istics or qualities; sounds of the voice and of musical instruments, particularly when both or several of each are effective, are made up of not merely given fixed frequencies but rather of fundamental and harmonic or component frequencies and to lose one or more of the latter is to change the quality or naturalness of the original tone; the greater the Volume of the sound, and in theatres and auditoriums the volume is of great magnitude, the greater is the effect of the resultant distortion or departure from the original tone.

Furthermore, by the apparatus described above, I am enabled to obtain such a high standard of operation of the photoelectric cell and to make such efiicient and effective use thereof that the amplification required of the amplifier 25 (Figure 4) to produce a given volume of sound in the loud speaker 26 is but a small fraction of what is required with systems or apparatuses heretofore known; for example, I am enabled to achieve the same required volume of sound in the loud speaker 26 with an amplification, by the amplifier 25, of only about t or 15% of the amplification necessary with certain here-tofore known apparatus. This important feature makes it possible to diminish first cost greatly in that the amplifier need be of only much smaller capacity while the energy consumption in and maintenance cost of the amplifier are vastly reduced.

A significant and important feature also is the high efiiciency of action of the optical system a whole; for example, it is standard practice, particularly in theatre installations to utilize a 32 watt incandescent lamp bulb having a rating of 4 amperes at 8 volts. This requires the provision of storage batteries or the like to furnish the low voltage of 8 volts and necessitates the installation of battery-charging equipment, not to mention the requirement of maintenance of such equipment as well as of the batteries themselves. I have achieved excellent results, such as those pointed out above, with the use of a lamp bulb of as low as 12 watts, using a lamp having a voltage rating of 8.0 volts and a current rating of 1.40. Thus, the energy consumption may be cut virtually in half with greater than corresponding savings in storage battery equipment and maintenance.

I have above pointed out that the lamp socket 28 (Figure 1) does not require critical adjustment. With heretofore known apparatus, particularly the apparatus employing a slit, generally a slit of a width approximating as closely as possible 0.001", every time that a lamp bulb burns out and has to be replaced, the new lamp bulb with its socket has to be carefully adjusted not only to get the filament centered on the optical axis but also positioned at a critical point along the optical axis, and the adjustments necessary to achieve these requirements are cumbersome, tedious and time-consuming; so much so that various cumbersome expedients, such as duplicating equipment, are resorted to in practice. These so-called exciter lamps are intended to be of standard and uniform construction; nevertheless, even such variations or tolerances as cannot be avoided in manufacture completely disrupt the operation of known equipment with the need for adjustments as just pointed out. With my apparatus, however, the element X inherent- 1y, because of its above-mentioned characteristics, has such a wide range of action with respect to the position of the luminous filament with respect to which it acts as a secondary light source, that no such adjustments need be made. A lamp socket with a lamp bulb of given type therein, once adjusted or set at or even only near the optimum point with respect to the optical axis A-A need not thereafter be reset or readjusted when the lamp bulb has to be replaced. Thus the burning out of a filament requires no more interruption of service than is needed to snap the one bulb out of the socket and snap a new bulb in its place; no readjustments are needed and it is entirely unnecessary that one be skilled in the heretofore known art of replacing and adjusting exciter lamps.

The above sets forth some of the important practical aspects of my invention. It might be noted, however, that element X above described, as well as related coacting parts, may be varied to meet particular conditions or circumstances of use. For example, I have above pointed out that the radius of curvature of the cylindrical surface 44 of element X is, in the illustrative example above assumed, 4;; this cylindrical surface, however, might be given other radii of curvature. For example, it might be given a radius of curvature of 5, or less or a radius of curvature of or more; one determining factor is the range of spacings physically intended or available in a given sound reproducing apparatus; for example, the shorter that it is desired to make such spacings along the optical axis A-A, as for example the spacing C of Figure 4, the smaller should be the radius of curvature of the cylindrical surface of element X.

The optical system above described, however, may be embodied in various other forms of which I might mention a few by way merely of example. For example, I improve the action and result if I make the curvature of the curved faces 44 and 45 (Figures 8 and 8c) parabolic instead of truly cylindrical, while retaining the relation between the axes of curvature. Also, for example, I might make the curvature of the curved face 45 of Figures 8 and 8d spherical, as indicated at 45 of Figures 9a, 9b, and 90. Or I may, in any of the forms above-mentioned,

give the curved surface 44 a two-fold curvature as is shown at 4 3 in Figures 10a, 10b, and 100 from which it will be seen that the surface 44 in vertical section (Figure 100) is cylindrical or parabolic in curvature while in horizontal section (as is apparent from Figure 10a) the surface thi may be given a curvature of fixed radius or of varying radius as in a parabola.

Or I might embody the element X in the form shown in Figures 11, 11a, 11b, and llc in which I have retained the curved surface 45 (which may be modified as above described in connection with Figures 8-100) but instead of providing a concave active surface juxtaposed to the surface 65, as in these figures, I shape element X to provide a convex surface 51, the convex surface also having its axis of curvature at fight-angles to the axis of curvature of the face The surface 95, however, may be given various shapes as above described in connection with Figures 8-100 while the convex surface 5? may have its curvature of such different forms as I have above described in connection with the concave surface 44 of Figures 8l0c.

I do not desire or intend to be limited or restricted to the precise forms above described which are set forth solely by way of example. With such forms I am enabled to meet various requirements or peculiar conditions met with in practice and am enabled to achieve effectively such results as I have briefly outlined hereinahcve. For example, the curvatures of the lightreceiving surface and of the light-emitting surface may be varied one relative to the other to better suit the shape of any particular primary source of light that it may be desired to employ even though any one form as already above mentioned is capable of very efficient and effective functioning almost irrespective of the form or shape of the initial or primary source of illumidescribed in connection with, Figures 2 and 4,

will be clear in view of what has been set forth above. It might at this point, however, be noted that many features and actions of my invention may be achieved without the presence of, or shape of aperture in, the diaphragm 55 of Figures 2, 3, and 4, for example. I may, for example, change the shape of the aperture in the diaphragm or dispense with the diaphragm entirely. However, by dimensioning and positioning the aperture (with respect to the other elements, of course) as above described in detail in connection with Figures 2, 3, and 4, I have found that I am enabled to obtain best results and to achieve a heretofore unachieved ratio of energy output of the photoelectric cell to the light effective in the optical system.

I have earlier hereinabove mentioned that the optical system of Figure 2 is sealed; to effect this sealing dependably I prefer to employ, where threaded parts are used, a small pitch of thread and to seal the threaded parts as well as any of the glass-and-metal joints with a suitable cement. I have found a satisfactory cement to comprise a mixture of zinc oxide and water glass or a mixture of finely powdered litharge and glycerin-e, for ealing such joints. Such cements are not affected by heat, moisture, oil, or vapors thereof and thus the effective glass parts of the optical system are dependably sealed against such foreign matters as these and are dependably kept clean. Thus, I eliminate the need for having to clean these parts or to arrange them so that they may be easily disassembled for cleaning purposes.

From the foregoing I believe the practice of my invention in so far as sound reproduction is concerned will be clear. As for sound recording, what I have stated above makes clear how I am enabled to achieve, at the intersection of the beam of light with the film, a straight line extending crosswise of the sound track but of very minute dimension; I have above pointed out that I can achieve a thickness of beam at this intersection of 0.0003". This is an important desideratum in that I am enabled to cut the higher frequency film records of sound with such nicety and precision that virtually none of the important contribution of the high frequencies to the quality and naturalness of sound is lost. By means of my invention, moreover, I am enabled to record sound on film with greater faithfulness and naturalness than has heretofore been possible and in Figure 12 I have diagrammatically indicated one of various possible embodiments of sound recording apparatus embodying my invention.

Referring then to Figure 12, I have shown at 58 the film on the sound track of which a film record like that of Figure 5 is to be made; the film 58 is guided and driven along a predetermined path or in a fixed plane by any suitable mechanism which may include driving and driven sprockets 59-69. At 5! I have indicated a suitable sound responsive device suitably related to a suitable means for affecting the beam of light which I project upon the sound track of film 58. Conveniently, the device 6| takes the form of a microphone or the like adapted to vary the output of a suitable source of current 62 in accordance with the frequency of the sound striking the device 6!, whereupon a suitable amplifier 63 suitably amplifies the resultant audio frequency currents in order to correspondingly affect the electrodes of a suitable Kerr cell suitably related to suitable Nicol prisms, all of which are diagrammatically indicated at 6 1, conductors 55 and 5B connecting the electrodes into the output circuit of the amplifier 83.

The Kerr cell, interposed between two Nicol prisms is, with the latter, inserted in the path of light originating from a suitable primary source 61 and directed to and upon the sound track of the film 58.

Interposed between the source of light Si and the Kerr cell and Nicol prism assembly, is a light tube diagrammatically indicated at ME] and em bodying therein a light-ray controlling system substantially like that above described in connection with Figures 2 and 3.

The light tube MD of Figure 12 has mounted therein element X and nearest the primary source of light 61, thus to form secondary and tertiary sources of light as was already above described in detail. To the left of element X is a diaphragm 55 with a square aperture i55a therein and to the left of the diaphragm are achromatic projecting lenses M9 M9 and l53-l54 substantially like lenses it--59 and Sit-54 of Figure 2.

The rectangularly-cross-sectione-d beam of light then passes through the Kerr cell and Nicol r assembly where its intensity is v cordance with the audio frequency current output of the amplifier E3, all while the film 53 is being moved at a suitable speed, whereupon the beam of light, now varying in intensity at an audio frequency rate, emanating from the assembly 64 is converged by any suitable lens or lens system $8 onto the sound track of film 58, thus to form a sound record like that shown in Figure 5.

With this system and method of sound recording, it being understood that I may employ other means, such as a vibrating mirror, for affecting at an audio frequency rate the actinic action of the light on the film, I am enabled to use virtually any shape of initial light source 61 in view of the action th reon of the element X as will now be clear in view of What I have set forth in detail in connection with the sound reproduction. Moreover, the so-called image (the intersection in a line of the light beam with the sound track on the film 53) is, like the so-called object (the secondary and tertiary sources of light) accurately and geometrically rectilinear in its boundaries; this characteristic, true of my method and apparatus for sound recording as well as of my method and apparatus for sound reproduction, will be better understood when I point out that, where a minutely dimensioned slit is employed the image and/or the object are not rectilinearly bounded but are bounded by irregular zigzag or saw-toothed lines; the latter effects are due to the fact that it is impossible physically to achieve light-bounding surfaces so smooth that they will not provide a multitude of light-reflecting or light-affecting minute surfaces of various angles to each other, being oftentimesaccompanied by a prismatic action in breaking up white light into various component colors.

The resultant stray light and the resultant irregularly shaped beam prevent the achievement of precision of action on the film, either in reproduction or recording. These detrimental ac.- tions, however, are entirely absent with my systom and apparatus in which, virtually no matter what the shape of the incandescent filament or other light source, I achieve, without mechanical restriction or obstruction, a cross-section of beam of light that is bounded by geometrically perfect lines, free from such irregularities and actions as have just been mentioned.

This characteristic, therefore, makes it possible for to record with perfect precision and this is ..rticularly important where the higher frequencies, such as 8060 cycles per second or above ar concerned. A contributing factor to faithfulness recording and to faithfulness of reproduction is also the small thickness of beam which I am enabled to achieve, where it intersects the film.

From the foregoing, the practicing of my invention, I believe, will now be clear and it will be seen that I have provided a method and appafor recording and reproducing sound in oh the various objects hereinbefore set forth a" well as others, together with many thoroughly ctical advantages are successfully achieved. I wish again topoint out the uniformity of frequency response. which I have been able to achieve; ii, for example, in the reproduction of sound from the film record as above described, apparatus is analyzed and tested in actual operation, it will be found that, due to the various characteristics and coactions of the various coacting parts, the energy or power output and hence the volume of ultimately reproduced sound remain substantially constant over a range of frequencies from at least 50 cycles per second to over 8000 cycles per second; this is a performance which it has heretofore in practice been impossible to achieve though many attempts have been made to achieve this result. Certain important effects of this result upon the quality or naturalness of reproduction I have already hereinabove mentioned.

Furthermore, the apparatus is characterized by highly desirable simplicity of control or operation, an example of which I have already mentioned above in connection with replacement of a burnt-out exciter lamp. Furthermore, the over-all efficiency is of heretofore unsurpassed magnitude as will be clear from even only a brief consideration of the small energy input to the eXciter lamp and a comparison thereof with the exceedingly small amount of amplification of the photoelectric cell output to give a volume of sound comparable to or even in excess of heretofore known practical methods.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope f the invention, it is to be understood that all matter hereinabove set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

1. In apparatus of the character described, in combination, means having a light-sensitive surface, a source of light, a film having a sound record thereon, means for guiding and moving said film along a. path interposed between said source of light and said surface, and means for causing light from said source to intersect said sound record in a straight line and to strike said surface a iarge rectangular area, said means comprising light-ray controlling means for converting said source of light, irrespective of its shape, into a secondary source of light that is relatively thin in the direction of the length of the sound record and relatively elongated in a direction transversely of the sound record, said ray-controlling means having the characteristic of converging light rays from said source of light in said firstmentioned direction and of diverging light rays from said source in said second-mentioned direction, projecting lens means interposed between said secondary light source and said film, said film being at one focal point of said lens means, and a diaphragm intermediate of said secondary source of light and said projecting lens means, said diaphragm having a square aperture and being spaced along the optical axis a substantial dis tance from said secondary source of light and being positioned at the other focal point of said projecting lens means.

2. In apparatus of the character described, in combination, means having a light-sensitive surface, a source of light, a f lm having a sound record thereon, means for guiding and moving said film along a path interposed between said source of light and said surface, and means for causing light from said source to intersect said sound record in a straight line and to strike said surface in a large area, said means comprising light-ray controlling means for converting said source of light, irrespective of its shape, into a secondary source of light that is relatively thin in the direction of the length of the sound record and relatively elongated in a direction transversely of the sound r rd, said ray--controlling means having the characteristic of converging light rays from said source of light in said first-mentioned direction of diverging light rays from said source in said second-mentioned direction. said lightray controlling means including a glass element bounded by two substantially cylindrical surfaces, one of which is of relatively large radius and has an axis substantially parallel to said first-mentioned direction and the other of which has a relatively small radius of curvature about an axis at right angles to said first-mentioned axis, and means interposed between said element and said film for projecting the secondary light source through said sound record and onto said lightsensitive surface, said sound record being substantially at the focus of said projecting means.

3. In an apparatus for recording sound on film, in combination, a sensitized film, means for moving and guiding said film along a certain path, a source of light, and means for causing light from said source to strike said film in a thin straight line, said last-mentioned means comprising light-ray controlling means for converting said source of light, irrespective of its shape, into a secondary source of light that is relatively thin in the direction of the path of movement of the film and relatively elongated in a direction transversely of said path of movement, said ray-controlling means comprising a glass element bounded by two substantially cylindrical surfaces, one of which is of relatively large radius and has an axis substantially parallel to said first-mentioned direction and the other of which has a relatively small radius of curvature about an axis at right angles to said first-mentioned axis and having the characteristic of converging light rays from said source of light in said first-mentioned direction and of diverging light rays from said source in said second-mentioned direction, and means responsive to sound for effecting an audio frequency change in a characteristic of the beam of light striking said moving film.

4. In an apparatus like that claimed in claim 3, in which radius of curvature of one of the cylindrical surfaces of the glass element is on the order of 0.125" and the radius of curvature of the other is on the order of 0.75.

5. In an apparatus like that claimed in claim 3 in which that surface of said glass element that is nearest the light source is convex and of large curvature about an axis parallel to the direction of movement of the film and the surface nearest the film is of a curvature about an axis at right angles to said first-mentioned axis.

6. An apparatus like that claimed in claim 2 in which that surface of the glass element which is nearest the film is concave.

'7. An apparatus like that claimed in claim 2 in which that surface of the glass element which is nearest the film is convex.

8. An apparatus like that claimed in claim 2 in which the curvature of at least one of the surfaces of the glass element is parabolic.

9. An apparatus like that claimed in claim 2 in which the surface of the glass element nearest the source of light is spherical.

10. An apparatus like that claimed in claim 2 in which the surface of the glass element that is nearest the film also has a curvature about an axis parallel to the path of movement of the film.

11. An apparatus like that claimed in claim 3 in which the sound-responsive means includes a Kerr cell and Nicol prisms between which and the secondary source of light there is interposed a diaphragm having an aperture therein that is rectangular for controlling the cross-section of the beam of light upon which the Nicol prisms and Kerr cell act.

12. An apparatus like that claimed in claim 3 in which there is provided a diaphragm having a rectangular aperture positioned in the path of light rays originating in said secondary source of light for giving the beam of light a rectangular cross-section.

13. An apparatus like that claimed in claim 2 in which the two substantially cylindrical surfaces are spaced in the direction of light-projection and have radii of curvature on the order of 0.125 and 0.75" and in which the glass element is made of crown glass having an average index of refraction of 1.52 and a dispersion factor for the D-line of 64.0.

14. In apparatus of the character described, in combination, means having a light-sensitive surface, a source of light, a film having a sound record thereon, means for guiding and moving said film along a path interposed between said source of light and said surface, and means for causing light from said source to intersect said sound record in a straight line and to strike said surface in a large area, said means comprising light-ray controlling means which include a glass member bounded by two surfaces spaced in the direction of light-projection, the surface of said glass member that is nearest the film having a curvature about an axis parallel to the path of movement of the film and its other surface being shaped to cause said member to diverge light rays in a direction transversely to the path of movement of the film.

15. In apparatus of the character described,

in combination, means having a light-sensitive surface, a source of light, a film having a sound record thereon, means for guiding and moving said film along a path interposed between said source of light and said surface, and means for causing light from said source to intersect said sound record in a straight line and to strike said surface in a large area, said means comprising light-ray controlling means which include a glass member bounded by two surfaces spaced in the direction of light-projection, the surface of said glass member that is nearest the film having a radius of curvature on the order of 0.125, the curvature being about an axis parallel to the path of movement of the film and its other surface being shaped to cause said member to diverge light rays in a direction transversely to the path of movement of the film, said glass member having an average index of refraction on the order of 1.52 and a dispersion factor for the D- line on the order of 64.0.

16. In an apparatus like that claimed in claim 15 in which there is a tube-like member in which said glass member is mounted, said tube-like member being positioned between the source of light and the film, said glass member having ex tensions or portions such that it is peripherally substantially circular for reception within said tube-like member, said extensions or portions of said glass member being opaque,

17. An apparatus like that claimed in claim 15 in which the spacing between the source of light and said glass member is on the order of 1.25" and in which the spacing from the glass member to the film is on the order of 2.250".

PAUL SAFRANSKI.

CERTIFICATE or COBRECTION.

Patent NO. 2,037,73 April 21 1956.

PAUL SAFRAI'SK It is hereby certified. that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 9, first 1 4 5 respectively, for the reference numcolumn, lines 59 and 44-, cieims i eral "5" read 2; and that tLe said Letters Patent corrections therein that the same may conform the record of the case in the Patent Office Signed and sealed. this 4th of August, A. Do

should be with these Henry Van Arsdale (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent NO. 2,057,759. April 21, 1956.

PAUL SAFRANSKI It is hereby certified that error appears in the printed specification oi" the above numbered patent requiring correction as follows: Page 9, first column, lines 59 and 44., claims 4 5 respectively, for the reference numeral "5" read 2; and that the said Letters Patent should. be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of August, A. D. 1936.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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